If you get into an argument with someone and they keep coming back for more, they probably enjoy it in some way. Just make it clear that while you disagree, you still respect them as a person. You'll probably be fine.
Rarely does one get into an argument with a whole group. That's a different game that is best avoided.
The social dynamics of groups are really interesting.
I'm in a Facebook group for vegans, where people continually justify eating things that have meat byproducts in them because they're convenient or they "don't believe its actually there" even though something is labeled as such. Its quite comical. I also just stopped participating because it was ridiculous.
Rarely does one get into an argument with a whole group. That's a different game that is best avoided.