think there's two issues here. first, plainly racist attacks (of the type Slothrop was referring to), and secondly attacks on religion which are evaded by the suggestion that they carry racist overtones (which of course may or may not be true, depending upon the circs, but certainly is sometimes not true, and the attack is strictly upon religious issues).
And then, yes, thirdly, there's N-Dubz. But without getting into the details of that case, it's certainly true that non-white people being silenced when they allege racism that actually has occurred, is far wider a problem than people 'hiding behind' accusations of racism. And, leaving rights or wrongs aside for a minute, the latter would never happen/be an issue were it not for the extraordinary prevalence of the former.
Also, without getting into the truth of anyone's account in that N-Dubz case (the article seems incomplete, and naturally doesn't present the evidence in full), it is quite possible (and I would argue in this case, extremely likely) for the two following to both be true: (i) the N-Dubz guy did sexually molest this girl; and (ii) there was racial stereotyping in the court room, quite apart from the facts of the case. I.e. yes, he deserved to be convicted, but the decision of the jury was made more quickly than it should have been/for the wrong reasons, based on the preconceptions held by some of its members, preconceptions that are extremely common in the UK. Which would make what he said afterwards both an excuse and also a reflection of a truth (just not the truth that he was alleging, that he was innocent of molesting the girl).