[Rotareti]

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.

[Whitestrake]

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.