It’s the difference between supporting the action and understanding it.
You can formally not approve of someone’s action, without saying it’s “completely wrong”.
You can understand and express disappointment that the proper channels had failed, that “with consent” was an exhausted option.
You can say you don’t condone the action, but understand the anger and frustration behind it.
You can say it’s “completely wrong” that it had to take this action to remove a statue honouring a slave trader.
Again, as the leader of the Labour Party, he’s not gone on air unprepared, so that means he decided to use the words he did. And for that, he’s rightly being criticised.