Does hosting guests at home with meat and alcohol (because they are fond of it) amount to aiding the guests break their Sila?

So often, people try to directly or indirectly force their religious beliefs on others (by not serving alcohol for instance). But I think that by doing so, you strain your friendships. No two people share the same exact beliefs about everything. But by being friendly and easy-going, you may teach others your beliefs and learn about their beliefs. Often times, different beliefs within the same religion will seem conflicting at first. For instance, Christians follow Drink no longer water, but use a little wine for thy stomach's sake and thine often infirmities. But there's also And be not drunk with wine, wherein is excess; but be filled with the Spirit. These verses seem to be the opposite of each other: Drink or not drink. But by drinking in moderation and not in excess, one can live in harmony with both verses. I'm not saying to convert to Christianity. I'm just sharing my beliefs and trying to learn yours.

As someone has already mentioned, a social gathering of any sort is for people to meet, share their troubles and joys and to unburden themselves from their daily routine. The food and drink served is secondary.

From your question it seems like your friends are important to you and so are your beliefs. It is not impossible for them to coexist peacefully.

Indeed you may think that by serving them meat and alcohol you are aiding them break their Sila but by forcing them to abide by the "my house, my rules" you would be seen as trying too hard to get them to see your opinions.

Losing friends just because they don't think like you is also not an option I'd suggest - you're never going to find people who think exactly like you do, and also it would be uninteresting. I'd find nothing new to learn if I wasn't in the company of people who were not like me.

I'd suggest a gentler approach. If you are happy to continue serving meat and alcohol, maybe talk to them about how you think being a vegetarian has been beneficial to you in more ways than one, how it is probably better for the environment and to our health, talk about some really delicious vegetarian dishes you managed to cook, talk about your beliefs and how they are important to you and gradually suggest going for a vegetarian only meal the next time they are around.

This way they will gradually and hopefully grow to respect your beliefs. It is a slow process but it bears more fruit than imposing a meat and alcohol ban or losing your friends.

According to the Talaputa Sutta:

Any beings who are not devoid of passion to begin with, who are bound by the bond of passion, focus with even more passion on things inspiring passion presented by an actor on stage in the midst of a festival. Any beings who are not devoid of aversion to begin with, who are bound by the bond of aversion, focus with even more aversion on things inspiring aversion presented by an actor on stage in the midst of a festival. Any beings who are not devoid of delusion to begin with, who are bound by the bond of delusion, focus with even more delusion on things inspiring delusion presented by an actor on stage in the midst of a festival. Thus the actor — himself intoxicated & heedless, having made others intoxicated & heedless — with the breakup of the body, after death, is reborn in what is called the hell of laughter.

There is a discussion in this answer:

The Buddha quote from the sutta says that anyone with some passion, aversion or delusion, reinforces it by watching the actor's performance. The actor too is intoxicated with emotions due to getting into character to play the role. And by acting out the role on stage, the actor has the intention of getting the audience to experience the same emotions. This intention is karma.

So, this applies to your question too, if you had the intention to satisfy their craving for alcoholic intoxication, which is not allowed in the five precepts.

Meat on the other hand, may be a different story according to the Theravada tradition, based on this article and this question, as picking out meat from the supermarket does not count as having the intention of taking the animal's life, since it was already dead and you did not select it to be slaughtered.

While it could be argued that serving meat satisfies the craving for its taste, but then again, meat and any food is required for our physical sustenance, regardless of craving for sensual pleasure. So, this is OK in my opinion. Of course, good vegetarian food is also sufficient for physical sustenance and meat is not required (in most cases).

Alcohol on the other hand, is not needed for physical sustenance. It is used only for intoxication.

On the subject of food, I do not see any issue with not serving meat. I would not expect any of my vegetarian friends to prepare meat for me.

With alcohol, the same applies, but because it's more "expected" in a party (depending on how it's advertised to the invitees), it would make sense to mention this and allow people to bring their own. "Alcohol will not be served but feel free to bring your own." This reduces the extent to which you could be seen as an "enabler" of their "sin".

"Bring your own" can also apply to food in some cases - when hosting a barbecue for example, you could provide vegetarian options while allowing guests to bring (and if necessary, cook) their own meat. You may need a separate grill in that case though.

Party is made fun by people sharing their love and life experiences with each other, not by meat and alcohol.

More importantly, in this case, I think you should uphold your spirit and not bend to your friends' opinions. Do not be afraid to show your friends who you really are, your real value system. Living authentic life is better in long-term, than pretending to be someone else out of fear of losing the little you have.

No need to boast or preach. Just do what you truly believe in, they will see and ask, and then you can answer.

"So, when I host a party at my place, it becomes obligatory of me to host them with alcohol and non-vegetarian food (bought from a restaurant). "

I don't see how it is obligatory. You could serve delicious vegetarian food and non-alcoholic drinks. If you take your Buddhist precepts you are not supposed break them yourself or encourage others to break them. I think your instincts on this are correct.

Would it be so boring? Have you spoken to your friends about this? Why not raise the subject and see what they say?