"Proship" includes basically three "beliefs"
1. Ship and let ship (your ships don't harm me and vice-versa) and YKINMK (your kink is not my kink, and that's okay; my kink stories don't harm you and vice-versa);
2. Harassment over fiction is not acceptable;
3. Censorship of fiction is not acceptable either.
You can still say "I think 50 Shades of Grey is a bad representation of bdsm and the relationship is abusive but portrayed by the author as romantic and I think that's a bad thing" while also not wanting the book to be banned or the author harmed. Personally I think proship should also include "fiction is not education". I think think every single bdsm porn novel should include detailed information on how to do bdsm in a safe and proper way, because reading that is not very fun. But I can still think that books with very dangerous depictions of bdsm suck ass. Those thoughts are not mutually exclusive.
TL;DR you can call yourself proship if you want, in my opinion ¯\_(ツ)_/¯
Yeah.....
As a Christian, I definitely come to shipping with a lot of beliefs that don't necessarily fit neatly into fandom culture. Take for example incest shipping, a type of shipping that a lot of people think is okay but a lot of other people think it's morally repugnant. I personally also think it's morally repugnant. However, I am also coming from a background where I pretty much expect everyone around me to reject almost all of my sexual mores, so it's not really that shocking to me to see people out there who think shipping incest is okay as long as it's not really happening.
I have to shut my mouth about other people's behavior so often that keeping myself to myself in the context of shipping is not such a huge ask. It actually surprises me more when people feel entitled to go around acting like the morality police as though no one has ever resisted them before.
As a Christian, I believe that what people think about does matter and is a moral issue. I believe that reveling in sin is bad. That means doing things like reveling in incestous pairings. It affects and corrupts people's minds to do this. Therefore, I can't unequivocally agree to a lot of proship sentiments that seem to think fiction has no relationship to reality or people's character.
HOWEVER... harassing someone never helped them repent, and I also don't believe in government censorship.
Now if I were in charge of AO3, I don't know if I could bring myself to allow p*dophilic pairings on there, but fortunately for all of us, I am not in charge of AO3, because I know that an archive has to function in a certain way in order to exist. And you know what else? I'm also really glad that AO3 openly allows and categorizes these types of ships... because if they didn't, they would be hanging around in the archive untagged and I would be forced to just stumble on them at random! Instead I can avoid them at will. So it's a genuinely complex issue.
Add to that that a lot of antis are clearly insane about what they consider to be "incest" or "p*dophilia" and they've made a really bad name for themselves and no one wants to be associated with them. So yeah.