I'm pretty sure it should never has been a penalty (and i'm a Spurs fan).
But what people forget is that City equalised and that afterwards Spurs scored another goal.
One could argue that a draw would have been a fairer result, but City let that slip away too and Eriksen's winner was a very good goal.
Not loosing the match was more important for both teams than trying to win. One could understand that from Spurs: young team having got 18 goals against in the last 6 matches against City, being the away team...
I don't understand that from City: being the home team, having scored 18 goals in the last 6 matches against Spurs, being the big title favourites, and having lost against Leicester...