It is never okay to harm someone because of their beliefs. No one chooses what to believe; pointing a gun at someone’s head and telling them to believe something can only make them lie, at best. Today’s events should make this perfectly clear.
No one should be discriminated against or punished in any way for their beliefs, since their beliefs are not up to them. Beliefs are a product of which arguments a person has heard and the experiences which have shaped the lens through which they see those arguments, neither of which a person can choose.
Although no one should face punishment for their beliefs, we still have to prevent dangerous beliefs from leading to dangerous behaviors. Using the above line of reasoning to conclude that we can’t discriminate against someone whose beliefs are that it is okay to kill innocent people would be absurd. Of course we need to do our best to convince people such beliefs are wrong, lest we allow terrible consequences to develop unchecked until it’s too late.
Although that was an extreme example, it remains true that criticizing beliefs is a necessary part of what it means to live in a civil society, where the best ideas flourish. Yet there is absolutely no reason to kill, harm, or even hold in contempt those who believe different things than we do. And it certainly is possible to advocate for the best beliefs and condemn the worst beliefs without directing anger at those who hold them. This, I think, is an idea worth spreading. So much of the violence in this world results from a failure to realize this.