You're both right, of course, that there are a range of situations to consider. People tend to associate with others with whom they share common beliefs and attitudes. That applies to churches representing different religions and sports bars where people assemble to root for their teams. That's pretty innocuous stuff where those affiliations are reinforced and validated by the others who congregate, and we assume that what they do in private reflects that commitment.
On the other end of the spectrum we say expressing hatred toward someone's religion, ethnicity or race is not permitted, even though that also is a belief or attitude. People who congregate in order to confront and denounce gays or protest at abortion clinics are also expressing their beliefs. I think all of those “beliefs and attitudes” are odious; the group behavior falls somewhere between extremes and is allowed by free speech rights, unless they physically attack or deny those people access to publicly available facilities. Let’s not forget that lynchings were not uncommon in the US even into the 20th Century and were often treated as
celebrations in town squares.
I find it sad and even a bit weird that state legislatures single out groups of people with particular physical characteristics
specifically to leave them unprotected from business or public accommodation or protection. Michigan does that with LGBT, other states are enacting "bathroom laws" targeting transgender people. Cities in Tennessee and other states have tried to block construction of an Islamic mosques, stretching local laws to cover their personal biases against that religion.
And this weekend we have another extreme expression this sort of hatred that I think makes us question how valid the basis of any sort of exclusionary or discriminatory "belief" is. The shooter in Orlando called 911 and swore allegiance to ISIS while he was walking around the nightclub shooting. He ended up killing about 50 people and wounding another 50 or so. He has been rightly denounced for his actions, but did he really do it for ISIS, or is there more to understand about his motivations?
From his father and his ex-wife, we are learning that he had a deep-seated hatred toward gays and a violent and abusive personality. His father says he chose the wrong way to express his hatred of gays. His ex-wife says she "escaped" their home and divorced him due to his violent temper, where among other things he would beat her if he came home and found that she hadn't done the laundry. A former co-worker says he routinely ranted about homosexuals to the point that he complained on numerous occasions to his boss and eventually quit because of his own safety concerns. No matter what anyone's beliefs are, I don't see how anyone could do what he did and not be emotionally unstable and predisposed to commit acts of violence. In this case (at the moment until there is more information) my sense is that he acted out of his own emotional problems and feelings of hatred and used ISIS for "permission".