It's seriously insulting that people seem to think that that is the only reason, nevertheless here is the video provided by jjoongiel0ve and translations by thatsdumb.
Hyesung: When we talk about a person with a kind heart (angel who goes around doing good deeds/선행천사) we can not forget about Jang Nara..
Tiffany: Aaah..
Hyesung: Like in the recent earthquake that hit China, she didn't hesitate in volunteering to help out the victims of Sichuansong.
Hyesung: She's been doing a lot of really good deeds, I'm really envious. I think its something that we all should learn from her.
Tiffany: Kekeke..
Hyesung: Why? Why are you laughing?
Tiffany: Kekeke.. Sorry.
Hyesung: But why?
Tiffany: You suddenly said ChanSong, the image of him going "Bop-a Bop-a~" came into my mind.
Hyesung: Aaaah..
Tiffany: And number one, we have Rain, who has recently debuted in Hollywood..
Kim Hyesung is the male host of SSGB (Sonyeon Sonyeo Gayo Baekso) on Mnet, he is still the host while Tiffany has been replaced by a Kara member.
Now that you've seen it for yourselves, make your own judgement. This has never been apologised for, unless SNSD fans refer to the cyber notice on SMtown.com, which really was the most insincere piece of work I have ever seen.
That is the only apology we've ever seen, by the way, so I really don't understand why people (SNSD fans) keep saying they've apoligised so many times.
It was addressed to "people who love SNSD", so really the people they insulted and their fans do not apply.