A controversial call, but he should know you can't rejoin the track and immediately block someone from passing you for position. It's classed as rejoining the track in a dangerous manner and regardless of the circumstances, it's a fair penalty.
Dirty tactics from vettel yet again, which can be dressed as innocence. He has history of such incidents and clearly he's no learning from them.
Also, it should be, and probably was taken into account that he actually increased the gap to Hamilton in the aftermath by doing so.
He can moan and be petulant all he wants, he's just pissed off cos he got caught out. He bottled it under pressure from Hamilton, then rejoins and crosses the whole track to prevent Hamilton a certain pass, nearly putting him in the wall all while extending his lead in the process.
The stewards had only one choice and a 5 second penalty was the correct decision 👍