Not sure what you mean. Anywhere I ever davened, schnorrers were treated respectfully. All the disrespect I ever saw was from them. I get it that their financial state is really bad, and that is their desperation.
I need to prepare cash before entering shul. If I take cash from my pocket to give a dollar, and the schnorrer sees a five or ten, I get badgered to give it to them. If I was short on giving maaser, perhaps this is a favor for me. But that has never been the case. The rudeness is still offensive, and it is not provoked in shul.