Why is free speech valuable to begin with? I would say its value lies in allowing under-represented groups to voice their issues without fear of persecution. Discussion of political problems from multiple sides brings out a lot of issues that we as a whole can work to resolve. Free speech is not valuable in itself, it is valuable because it accomplishes these things. Therefore, limits on free speech ought to be acceptable so long as they don't lessen its purpose for existence.For what? For speaking her mind? You know that your have every right to like or to hate anybody you want in my country. You have the right to express those opinions. People who disagree with you and don't think very highly of you also have the right to tell you what they think of you in return.
Maybe if she got into a brawl, some anger management would be in order. Jail doesn't do anything to fix the root causes of crime, and usually turns people into even more hardened criminals. That's a debate that warrants a whole thread of its own, though.
This wasn't a problem with what she was arguing. While I disagree with the idea that a country should be closed off to all immigrants, I'm fine with talking about the issue with someone who thinks differently. The issue was that she wasn't advocating for an issue. She was insulting people. She was not trying to advance a position, she was not backing up her position with reasoning or facts. She was insulting people to their face. This serves no purpose. It is antagonism for the sake of antagonism. I have no problem with limiting speech that only exists to incite people, even if they happen to be expressing an opinion within that speech.
If you want to advocate for something, go right ahead; I'm all for different opinions and talking things out and all that hippee crap. However, being a jerk should not be constitutionally protected. You want to debate an issue, do so without excessive use of ad hominem or remove yourself from the debate. If she wanted to preach about how England is no longer the glorious white anglo-saxon state it once was, that's fine (though she shouldn't do it on a bus where people are just trying to go home, but that shouldn't be legally mandated). However, she crossed the line and definitely deserved what she got.
I guess what I'm trying to say is that it should be legal to be a racist douchebag, but only in the context of a debate. Don't go around calling people n-words or whatever and then waving around first amendment protection as an excuse, because really, **** you.