Oh dear. Though I suppose it's better that you just don't understand relative vs. absolute frequency, rather than that you're trying to say it's fine that muslims rape at a higher rate!
Let's have a little basic maths, shall we.
I'd rather not use rapists though.
So...
Imagine a pack of dogs, some black and some white. If 10 black dogs bite people and 2 white dogs bite people, presumably you would think more black dogs had bitten people than white dogs. And you would, of course, be correct. But this does not mean that black dogs are necessarily more likely to bite people.
Imagine there were 100 black dogs in the pack, and only 10 white dogs.
10 out of the 100 black dogs have bitten people, which means 1 in every 10 black dogs has bitten someone, which means 10% of black dogs have bitten someone.
2 out of the 10 white dogs have bitten people, which means 2 in every 10 white dogs has bitten someone, which means 20% of white dogs have bitten someone.
And 20% is more than 10% (double, in fact), so white dogs are actually twice as likely to bite as black dogs. Even though black dogs do more actual biting in total, as there are ten times more of them.
So white men do more raping, as there are significantly more white men in the UK than non-white men. But proportionally, (some) non-white men are more likely to rape. Statistics have shown Afghans are around twenty as likely to rape as white men. But (luckily), rape isn't all that common and there also aren't very many Afghans in Britain. So a very few men doing something twenty times more often than something that's not done all that often, is not going to be a big number.
Hope this helps.
ETA Sorry, forgot to add quote - this is (obviously) to @nomas