Would I mind someone spitting in my mouth? I don't know. I could tell you how I feel about it, right after we have Connor McGuire spit in my mouth. -I think I'd either like it, or fight like hell to learn to like it.
On the other hand, I would be irritated if someone were to spit on their dick for lube. My reaction would be, "Dude, you can do a lot better than that. Buy some lube."