That is the view of BT Sport pundit and former Arsenal defender Martin Keown.
Bellerin was adjudged to have felled Watford attacker Richarlison in the box and Troy Deeney sent Petr Cech the wrong way to draw the game level.
Former Premier League referee Graham Poll says Richarlison dived but Keown says Bellerin did not react as if he felt he did.
“If that was me I would have been absolutely incensed,” he said.
“He didn’t seem to be really that bothered with it.
“We’ve seen it at full speed, maybe you can see why the referee has given it.
“But really from an Arsenal point of view, they just weren’t ruthless enough.
“(Mesut) Ozil has a great opportunity to put the game out of sight.
“And really the way that they score late goals, Watford, you knew maybe it was coming.
“Recent goals against West Bromwich Albion got them a point and they’ve done it again.
“Marco Silva, well absolutely incredible, best we’ve even seen from Watford in the Premier League and boy are there fans enjoying it.”
Tom Cleverley gave the Hornets a late 2-1 win with a stoppage time goal.