That's not people's point. Sorry but you're taking the wrong idea from the argument. The point is that there are no laws in the United States that demand private forums have any semblance of "free speech". It's not that it's "not illegal". It's just simply not a concept that has any laws backing it up.
People bring this up because if you have any background in constitutional law, you know that free speech is something that took a long time to define (and most people don't even know what it is...). It's a legal concept, not a societal one. So when you complain that Paypal isn't respecting your free speech, anyone with a background in law goes "???"
Free speech is a legal term. When you say "Free Speech" you're referring to a very specific set of laws and rules that apply to public entities in the U.S. - not private ones. If you're actually talking about a sociological concept, then preface it as such. And if you feel that the laws don't match up in the United States to our perceived values, then say that as well.
But as is, Paypal has nothing to do with free speech. If you want to talk about some other idea, that's not the legal concept of free speech, but how you want Internet companies to operate in the U.S. you need to preface your statement as such.
Otherwise it just comes across as if you don't know what free speech is, so people respond with the tried and true "Paypal isn't the government". They're not trying to shut down any possibility of Paypal being regulated in a way that matches our current definition of free speech, just correcting your improper use of the term (is it pompous? I would say it could be framed better.) In other words, ya'll are arguing circles around each other.