If we followed your line of reasoning a Muslim could insist that he should be allowed to exercise his right to freedom of speech in the pulpit of a Christian church. Nobody is silencing FEers, just politely requesting that they exercise their freedom of speech in the place set aside for that and not in a place set aside for something else.
Furthermore, the endless spamming by FEers has turned many people off even giving it a second glance, so the strategy is counter productive if the intent is to inform rather than annoy.