I've found over time that most of my friends from high school and college as well as most of my immediate and extended family are way to the left of me politically. I've considered myself libertarian most of my life but I definitely don't agree with big L libertarians on a lot of issues. A big part of that is the influence of my wife. It took close to a decade, but she finally brought me back to the Catholic faith I had nominally been raised in - even though I considered myself an atheist for many years. That was a case where we had very different beliefs, hers being much more conservative, but we still loved each other. I changed my mind from callously thinking that abortion is a great way to get rid of all the worthless people in the world to recognizing that it is inherently wrong and an evil act. That's probably not a topic I'm going to discuss with that random cousin on Facebook who posts nothing but left-wing political talking points. Although I have been able to have some of those discussions with old friends and family because they can't easily dismiss me as some random person on the internet. But we're not going to have the same friendship we did 15-20 years ago.
The person I would still consider my best friend, even though we've only seen each other in person maybe 2-3 times in the last decade, has very different political beliefs from me. But we can still talk about plenty of other things without arguing about our political beliefs. We respect each others opinions and don't waste our infrequent conversations on trying to prove the other person wrong of convince them that our beliefs are better. He's the socially conscious urban liberal and I've become the conservative religious family man. But, we can still laugh at how the rent for his 1-bedroom apartment is three times the rent for my 5-bedroom house or how he can't imagine having six young kids.
So I think it all depends on the people involved.
I think this is accidentally a very good example of why it's sometimes hard for liberals to be friends with conservatives.
I have no problem with you believing that abortion is a sin. None at all. I don't agree, but that's fully within your right to believe, and to order your life around that belief. As you correctly note, that's a
religious belief (not a scientific fact), and you have your freedom of religion written into the foundation of the constitution.
The problem comes when conservatives support
banning abortion for other people who need them. That is them, taking their religious belief, and trying to force everyone else to abide by them. That is them taking away other people's freedom of religion. See also gay marriage, or any host of other social issues.
Would you still be friends with your liberal buddy if he was trying to get the government to
force you to abort your 6th child? Probably not. That would be the opposite of abortion bans though.
It seems to me that generally "liberals" take the side of liberty, and "conservatives" take the side of illiberal "you have to do what I say and you don't have any rights only my rights matter". The one obvious exception is gun rights, where sure, conservatives are definitely more on the side of liberty.
I have no problem being friends with people that disagree with me as long as we agree on the core tenet of liberty, and their actions (including who they vote for) reflects that. And no I'm not some "taxation is theft" libertarian nut either. But if someone is actively trying to remove the constitutional freedoms from people not like them, that's something I would struggle to look past.