"Because, I'm not annoying them with unsolicited business proposals"
So this is a crime! More of that, something is unsolicited after your being told it is. Before that, as any normal human being has to say/propose something, believes has something intresting to propose.
"then I'd be fully prepared to be told to "piss off""
Im sorry, I havent yet dealt with cruelty.
"it's because they get unsolicited business proposals all the damn time, and are sick of it."
If it was you, would you react the same? Would you react like this to someone who might be not only a... spammer, but a customer of yours?
If the answer is "No I wouldnt react like that", please stop write.