I don't believe Keir starmer, a bloody QC, actually believes it is "not correct" to say only women have a cervix.
I dug up to check the precise transcript, cos I've seen this phrased various ways:
Marr: Is it transphobic to say that only women have a cervix?
Starmer: It is something that shouldn't be said. It is not right... But Andrew, I don't think that...
Marr: So Rosie Duffield should not have said that. Can you explain to people watching why she should not have said that?
Starmer: Well, Andrew, I don't think that we can just go through various things that people have said.
He didn't quite finish the thought - he kind of tried to change tack after "not right" - maybe realising what he was saying - so it's not clear whether he was going on to say it's "not correct", or he was suggesting it's morally wrong to say it (because it upsets people?)