I happen to be passionate about things that affect the lives of everyone. I just happen to care about everyone. The same thing is true of the people I agree with and the people I argue with. We want what's best for the USA.
So while our ideology might me completely different, our bottom line is always the same, make America better.
I am equally passionate about music. Music is the life thread of my life. I make a living in the music industry. I love being around and talking to people who love music as well.
I brought up a jazz thread once. I got, this is "Rock" page from a couple people. One person went so far as to say they don't like musicians who are in to jazz because they think they're better than everyone else.

Are we only allowed to talk about Rock Music in General discussion ? No, many topics come up.
Rockpage IS NOT subject to free speech because it is privately owned. But the owner has allowed free speech. Kudos to him.
I have a "scroll" on my PC. If there is a thread about thrash metal, I don't open it because it doesn't interest me. If there is a thread about hockey, Oprah or a host of other topics I'm uninterested in, I don't open them.
With that said, I agree - Don't cause threads to evolve in to political threads. Perhaps we could ALL agree to that. I mean, if someone opens a music thread or a hockey thread he doesn't want to see politics ! I do hope that that comes out of this anti politics thread. Let's respect those who don't want to read politics, please.
A funny story at our gig last night. RobTheDrummer (one of my political nemesis') stopped by to hear us. In the middle of a song I ask for a drum solo. I held up an extra pair of drum sticks and motioned for Rob to come up. He joined me in a duet drum solo. (Is it called a drum solo with two drummers?). Anyhow, it was very cool.
When we took a break Rob and I were shaking hands and laughing and thoroughly enjoying each others company. I think it was Colton who kept saying to other people, "Look at these guys, they're at each other's throats in Rockpage political threads, they butt heads all the time". (I paraphrased that.) Rob and I just laughed more. Politics really doesn't affect friendships. So if you think we all hate each other, nothing could be further from the truth. Like I said, we understand we both wants what's best for America.
So, in all, I don't have an answer for you. It's a shame if musicians have been driven away from Rockpage because of politics. Would membership activity increase with a "No politics" rule? I don't know. It is so easy to NOT open a political thread and so easy to NOT read them.
I do sympathise with the thread starter:
So let's agree to stop ADDING politics to non-political threads ! Not because we have to, but out of respect for them.