It doesn't matter if they're a hate group and other people get offended by what they say--hate speech is protected speech.
Depends on the country. For example: Canada.
http://www.filibustercartoons.com/index.php/2013/03/06/playing-with-free-speech/The cartoonist makes a nice comparison between the free speech laws in USA and Canada, that Canadian version specifically states that the civil rights are subject to “reasonable limits prescribed by law as can be demonstrably justified in a free and democratic society.”
Or like their supreme court said:
“Truthful statements can be presented in a manner that would meet the definition of hate speech, and not all truthful statements must be free from restriction...”
So not only can your "free speech" be limited if it offends someone, you can be forbidden from saying certain things that are "considered offensive" even if what you said is based on facts.
The examples used in the article actually are WBC and a similar attempt in Canada that got stopped pretty quickly.