I think what distinguishes Internet service provision from all the other “platform” aspects of the Internet is that Internet service has become a kind of baseline utility. Everything depends on it: your smart home devices, your security system, Point of Sale systems, etc. You can’t search for employment without it, your kids can’t attend remote school, etc.
We all understand that when someone buys advertising space in a newspaper, they are forming a contract with that newspaper, and the paper has to be a willing participant. But that’s not really how we think of utilities. I think we’d all be pretty unhappy if the electric company refused service to a facility, or if the water company refused to hook somebody up to the water supply, or the fire department refused to put out a fire, due to the property user’s political speech. Even if we deeply disagreed with that speech.
I think ISPs are a lot more like utilities, and a lot less like newspapers. If it’s that important, then write a law explaining exactly how and when ISPs are intervene by removing or refusing service in these situations, and defend the law in court. But don’t leave it up to ISP terms of service.