I think this view is partly due due the insane speech laws in Britain: you can actually sue someone for telling the truth about you if it causes damage to your reputation. They just don't value truth like America does.

A huge part of this trial was the accusation that Heard lied (with a little help) about Depp abusing her, when really it was the opposite, as evidenced by the verdict. In Britain, the same verdict could have been achieved even if Heard was telling the truth.

Not that the "expert" here aren't pieces of shit (as usual), but it's also a cultural thing.