Absolutely not. They should not be allowed inside the main shul unless they are davening. They SHOULD be allowed to ask people who are exiting Shul, for tzedaka.
I am equally upset by people who disturb the guests at a simcha, especially during a chuppah. I would rather the baalei simcha (myself included) would have arrangements with the caterer to give X amount of dollars out for tzedaka and charge me for it, but not allow people to come into the simcha and disturb the guests.