The proship label says nothing about what content a person consumes.
Proship means you have a "ship and let ship" mentality. The "pro" in proship doesn't stand for "problematic."
"Proship means you ship adult x minor." No it doesn't. Proship means you won't harass or belittle someone who does. Proshippers don't assume the moral values of another person based on fanfiction.
There are Proshippers who are uncomfortable with age gap ships, there are Proshippers who are uncomfortable with shipcest, etc. There isn't a human being on the planet who isn't squicked out by some topics and Proshippers aren't a monolith.