I think that rule is for all the forum.
I really don’t have a problem with discussing politics; I can take it or leave it. But I think if we want a forum where people are forever blocking and ignoring each other, then introduce politics. If we want a forum where much, if not all, blocking & ignoring doesn’t happen, then keep politics out.
Political beliefs and values are often more in the core of a person than religion will ever be. With political beliefs, someone might just give a simple opinion, and someone on the other side of the fence might see that opinion as a personal attack; an attack on their identity. They may feel threatened in some way, when no attack was present. It seems at times that someone’s emotional connection with politics can be significantly stronger and deeper than any connection with any religion they might have.
Unfortunately, at times, this type of thing can find its way into none political discussions too. People see an attack when none was given. I think it sorts out the children from the adults. They then turn it into an issue about the other person, when the issue might be themselves.
Get two opposing people like this, and it can very quickly become world war 3 within a forum. Empathy and understanding goes straight out through the window, if there was ever any there in the first place. Where politics is concerned, friends suddenly become enemies when one learns of the political views of another.