Upvote:2
For this question you can get clear answers by reading Kalama Sutta. In Kalama Sutta The Buddha said;
'Don't go by reports, by legends, by traditions, by scripture, by logical conjecture, by inference, by analogies, by agreement through pondering views, by probability, or by the thought, "This contemplative is our teacher." When you know for yourselves that, "These qualities are unskillful; these qualities are blameworthy; these qualities are criticized by the wise; these qualities, when adopted & carried out, lead to harm & to suffering" โ then you should abandon them.'
Upvote:3
Those rules you have mentioned are only for monks. They do not apply to lay people. Lay people can consume any type of meat even if the animal is killed for them, as long as they don't break the 1st precept.
Yes, you can try to explain to people who look down on you, saying that being vegetarian is merely a food preference in Theravada Buddhism. Mahayana Buddhism seem to recommend a vegetarian diet by default. But that is not an excuse to look down on someone. You might also come across some confused Theravada Buddhists who follow vegetarianism like a religion, even putting it above what's said in the Suttas. Such practices usually fall under Silabbata-paramsa. One gives up on that when one becomes Sotapanna. Trying to correct them might push them away from the Dhamma. You can always practice Upekkha alongside Metta in such cases.