It's not appalling. It would be appalling if he dropped his trousers and mooned in full view of the BBC News Channel, but he didn't.
He simply had the gall to walk around his place of work wearing casual attire - something which is commonplace in workplaces up and down the land in 2020. I am sat at my desk wearing a grey hoodie right now in actual fact.
It may not be to your taste, and that's fine. But let's keep things in perspective and not go overboard.