It might make sense to work through that as a priority. I've talked it over with my wife and parents, who have a different outlook. My mom is a neuroscientist; it's in her case that it's most disturbing not to reach the same conclusions. However, all have clearly come out in support; respecting my wishes and plans would take priority.

Well, you know, that's kind of what I expect from a relationship of love and trust: that it can weather some quirks of mine, not fall apart at the first such. I'd expect an initial "ugh" reaction to unexpected and offputting news on my part, but I would also expect them to keep right on accepting me.

The usual tactics should work: "I know it's weird but I have an online friend who's definitely signing up, and when we discussed his/her motivations they seemed actually quite reasonable, I'm thinking about it a lot".

If someone won't accept that you are an independent thinker and make your own mind about things, and thinks less of you for that - that in itself is telling something about the relationship; better know where you stand.