Try to remember that whenever someone says something ignorant (i.e. Plants suffer too or I'll eat extra meat just for you) that it is nearly 99% likely they are saying this because they see the world is changing around them and they are soon to be lumped with the slaveholders, Nazis and other oppressors of the past. History gradually makes its way towards justice and in every instance of oppression, those who participate in this oppression cling onto it dogmatically and blindly, ignoring all signs that they are on the wrong side. So, don't let it bring you down. Focus on the fact that they know they are terrified because we represent the future and they the barbaric past...
The future is bright! Just focus on that.