Upvote:2
The easy way:
Ask for scriptural evidence for the claim. There is no reference in any Hindoo scripture as an evidence to this.
The difficult way:
Show that it is not possible using Buddhist ideas of Annata.
Easiest way:
Stay away from these arguments. I know where this is coming from. This is not disprovable or provable no matter how much you argue.
Upvote:2
Like @Friedrick
say, just stay away from those useless arguments.
And remember one thing: the Dharma is not for arguing.