In some ways Athanasists (Athanasians) are as intolerant as the WTS.
I think it sometimes you have to remember that the debate of Athanasius and Arius has continued throughout history and the JWs are not the only Arians on the planet....... they are just the most vocal and recognized.
Arians can be found quitely keeping to themselves in many Christian religions.
Sometimes church attendance is only about fellowship..... with broad concepts of unity....(Hence all Christians profess Christ is the Son of God)