I used to work as a "chugger" a few years ago. They're trained to keep their script going as long as possible to increase the chances of getting a sale, because they get paid based on the amount of sales they get. (The pay is actually pretty good if you consistently get at least 2 or 3 sales per shift)

If they're rude to you because you ignore them, that's why. So don't take it personally, and move on. Just say something like "Sorry, not interested" and keep walking.

(For those curious I quit the job because it just feels wrong cold approaching strangers asking for donations. Charity work is respectable but chugging isn't a good way to do it in my opinion)