I find it mildly amusing that anyone here actually thinks "free speech" exists anywhere. Even in places with Constitutional protection of free speech - United States, Canada, virtually any Common Law country where its implied (*coughAustraliacough*) - there are limits on freedom of speech for a variety of reasons - public safety being the primary one. Various jurisdictions take that to different lengths. While yelling "fire!" in a crowded venue is the most oft-cited limit and is just as likely to get you prosecuted in most Common Law countries (which include the US, Canada, etc), some of those countries also have more stringent limits on hate speech - while Westboro operates openly in the US, their members can be denied entry to Canada because some of their actions cross the line of hate speech under Canadian law and they are therefore prohibited from entering Canada.
So - unbridled free speech does not exist in any country.
Now, to the matter at hand - as this is not a legal ban on these organizations but rather a political statement that they should pack up and go home, I have no problem with it. Frankly, I think the anti-vax crowd needs to be publicly slammed, humiliated, discouraged, and challenged as often as possible. I see nothing wrong with what the Australian Senate has done. It's somewhat ironic that a few of you Americans do, since the US is one of the most prominent countries in denying children access to public schooling in certain jurisdictions if they cannot show proof of vaccination (for the record, an approach I wholeheartedly agree with).