You could create an issue template that explains the rules. If people still file support issues, you close those with a friendly reminder text (copy/paste) in which you explain the reasons why this is not the place for support. If people still think this is rude, they have personality issues which shouldn't be of your concern.
Aye, and you'd be well within your rights to do so, but I am doubtful that this approach will preempt the majority of people assuming rudeness on your part.