I was just sitting at the mall taking a break from mall walking. A man walked over to me when I wasn’t even looking up. He said "I haven’t seen you here before. " I said I wasn’t really here to talk to people and got up and walked away. He said he would leave, he may even have said sorry. I said I was ready to leave anyway. In retrospect I think he may have just been slightly mentally challenged so I wish I had been a little softer, he did not turn out to be aggressive. Looking for suggestions on something still clear and firm but more polite? This scared me for some reason, I think how fast he walked up and sat down near me.
Editing to add a key detail, he sat down close to me which is probably what made me more nervous than I would have otherwise been. I appreciate all the thoughtful feedback I’ve gotten and interesting discussion.
Well, you got up. Point made. No reason to fear anymore.
I would not exactly answer to what he said, but say a different thing, maybe like “You want to sit here?” (polite on the surface, stating the obvious, but implicitly putting the focus on on his action, not yours)