My mum studied cults ("new religious movements" mum please don't tell me off) and her first and only rule of how to not get into a cult was "do not. Under ANY CIRCUMSTANCE!!! Debate them." Because they got debated into the cult and know the arguments that work.
So yeah that's why all those Alt-Right chodes are always yelling DEBATE MEEEEEEE every chance they get. Debate isn't a fair and reasoned discussion, it's an extremely effective recruitment tool.
You don't have to debate them. Nobody does.
this is ESPECIALLY true if you are at college or university and think you're hot shit. I mean maybe you are, but people who approach you to talk about politics or religion have all the facts they need in their pockets. You're just a rando who's good at molar calculations.
You can say no and you're not the lesser person. THEY came into YOUR space, you didn't invite them in.