It was a soft penalty but basically don't put your arms all over an attacker (or let him get the wrong side of you) and it won't be a pen.
I don't like this narrative that's creeping in (and amplified by Martin Keown) that intimates we've been hard done by all season. Sure there have been some really stupid referee calls (in particular the penalty against Saliba vs Brighton, the Rice red again vs Brighton and the Trossard red at the Etihad) but we've also benefitted from the same type of stupid calls at times too (e.g Spurs should have had a pen at their place, Calafiori's equaliser at the Etihad shouldn't have been allowed to stand, Lewis Skelly should have had a red at PSV). So has every club, it's just that fans tend to only remember the ones that go against them.
The refereeing is terrible in this country and it would be wise to factor that in and try not to fall foul of it and not give the refs a decision to make.
We all know we'll give away a marginal penalty vs Madrid over the 2 legs where our fans will be up in arms yet could also have been totally avoidable. Someone's going to have a nibble at Vinicius or Rodrygo and then be amazed that they fall to the ground in the box.
The reason we've not won the league this season isn't the refs. It's on the board not buying adequate attacking cover and a striker. It's so obvious that anyone can see it.