1) He's not banned for being a conservative, nor writer. 2) They (likely) did not order a cake with writing on it targetting someone. They just wanted a cake for themselves. IANAL, but I'm assuming the bakery got ruled against on grounds of bias crimes against sexual orientation.

He's not targetted for either being gay or conservative or any other personal trait other than on their service portraying a seemingly vile human being through targetted harassment of other user(s), which they deemed a breach of their ToS.