God is Lord

My problem is not what they want to have on their user page, but that they want to spam the category with their user page.

I see your point, and it's a good one. Objection withdrawn.

In similar vein, I see he's link-spamming back to his blog. Keep, delete, or let the no follow thingy do it's job?

Meh. We have nofollow.

Does it matter if he spams links to that intellectually brilliant webpage, How to Shut Up an Atheist?

Nope. There again, nofollow will take care of this.