Could I Have Some Friendship Advice Please?

[Caterpillar2012]

I'll try to keep this short
Basically, I was hanging round with some friends, i'll call them K M and C for privacy. K was on her twitter in school ( we are in yr 11) and she found a hate page about one of her favourite celebrities. Then at lunch i was with K M & C and they were talking about some gossip to do with their favourite celeb's band saying that he'd disappeared. I joke around saying " maybe its because the rumors were true" making a light hearted joke out of the situation because they were getting worried. They began to get offended so i said i was sorry and they carried on having a go at me.They started screaming at me and threw my lunch on the ground... K and M won't talk to me - it's really immature. EG i sit with K in English and she wouldn't share a textbook with me.
M has always been nice to me and is quiet when the others have a go at me. I have 1 other friend who i can talk to but she is always busy with art coursework, and i feel frustrated because they are treating me as if i am a bully. I quote" You're a racist!" Which makes me wonder... I'm the only black one and looking back K and M have been kinda off with me before...
Anyway today i tried to apologise and talk to K and she had a go at me, again calling me a racist saying she won't talk to me until i apologize and was cutting over everything i tried to say- so i got frustrated and left.
Overall I'm asking what should i do? I've never upset any of them before, I've never been a bully and i am by no means racist , i don't even care that much about celebrities, whereas they kinda obsess over them, Have i done something wrong? Or are they just being immature? and is it bad that i'm angry at them for treating me like this? And last question, should i even regard them as proper friends?
Thanks

[Confused Monkey]

I'm assuming you're all in year 11, just get some some new friends because they're acting like annoying pre-teens girls crying over their favourite celebrities. That's very immature behaviour and I doubt they will change their attitude in the next year or so. If they're cutting over you in conversations and doing, quite frankly, what i call bitchy actions, then its not worth your time and effort to try and make it right. Everyone's entitled to their own opinions. If you've already said sorry and explained that your comments were a joke, and yet they're still acting immature, then just move on.