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.


I have to disagree with some other responses–the combination of the statement and immediately walking away sounds rude.
Just say you’re not really there to talk to people, maybe add a “sorry”, and look away from the guy. Or you could have added “sorry” to the beginning of your statement. Really any little thing to show that it’s nothing personal.
If she wants to be more polite in the future in similar situations, I think your script is useful and I appreciate it. But I think since his behavior made her afraid, getting away quickly without concern for etiquette was the better move and she doesn’t need to feel bad about it. It indicated immediately, if her instincts were correct, that she wouldn’t be an easy target. If he was just trying to make a connection and fumbling, he discovered quickly she won’t give him one, so he could go sit next to someone else.
(It’s useful to keep in mind that he already was slightly rude by sitting down without a cursory “is this seat free” that would be a very basic manners for this situation. He didn’t, and it’s not evil or anything that he didn’t. But when she got up and left abruptly she was at the same level of rudeness. I don’t think either party needs to feel bad about it, tbh. Social fumbles happen constantly.)
Women don’t have to be polite in pursuit of their own safety.
I didn’t say we do.
I mean, telling OP she was rude and that she should’ve apologized to the guy is kinda saying we do have to be polite even if we feel uncomfortable.
I don’t think you had ill intent or anything.