There are quite a few different issues here. First of all, Allison Pearson, misrepresented, either intentionally or accidentally, the police visit. They did not say anything about a "non hate crime incident" but about an offence under the Public Order Act, which is much more serious.
Second, the tweet itself is undeniably racist. She accused two men she didn't know of being "Jew haters," presumably either because of the colour of their skin or because they were holding what she erroneously believed to be a Hamas flag (in fact it was a flag representing a Pakistani political party.)
Third, that tweet contained two errors - the misrepresentation of the flag and the incorrect assumption that the police officers were from the Metropolitan police.
In her case, I'd be deeply embarrassed to have made such errors, particularly as a journalist. Checking your facts before publication, even on X, is part of the job. That she then compounds it by publishing an article in the Telegraph saying, untruthfully, that she was accused by police of a "non-crime hate incident" is quite remarkable. Why couldn't she have phoned the police station to check, if she couldn't properly recall what was said?
I don't, as it happens, think the police should be investigating what people post on Twitter, however offensive, because on the whole I tend to err on the side of freedom of speech, however unpalatable that speech is. However, Pearson now has the gall to threaten everyone pointing out that the original tweet is racist with a libel action because she apparently lacks the wit to realise that sending out libel writs right left and centre fatally undermines her claim to be a champion of free speech.