Let me dissect the incidents so that I am clearer.
vs. Stoke - It's more of a coming together, where Xhaka gains control of the ball, but Allen runs into him due to his momentum. Gotta ask yourself how many time body blocks like these are given, especially in the penalty area?
vs. Bournemouth - Again, it's a little more stupid, but it's a coming together. And the referee ignores an almost identical incident on Bellerin from which Bournemouth score their third. If one is a foul and a penalty, then I can't understand the referee's thinking behind not awarding a foul on Bellerin. Hence I said unlucky.
The red card vs. Swansea was a joke, it was a tactical foul trying to break a counter, we see numerous attempts at these every game and there is hardly ever a sending off unless it's the last man making the tackle. The only difference is he does in with his feet rather that trying to rip the opponent's shirt off. According to the letter of the law, he was sent off for endangering an opponent, for which there is no case here.
The red yesterday also could have gone either ways with a different referee. Yes, he was airborne for a moment but when he makes contact (barely any) with Defour, his feet are on the floor. Rojo got away with a couple last month, Feghouli got his red rescinded for a similar challenge and if it wasn't for the trigger happy Jon Moss (who get's all his player background from the dailies I think), the result would have been different.