mmm. Well, have just sat here scratching my head and staring at the screen for ages...
I can't think of a pet hate. Hate is a strong word, isn't it?
I'm really not very easily offended and even when folks do or say things that are in direct contrast to my values, beliefs or what I have actually done, I tend to just acknowledge their right to speak or their perspective and just state my view. Funny thing is, I guess, I've never much felt that people agreed with me anyway so maybe I am just used to having differing opinions 

 or generally feeling misunderstood. LOL.
I dunno. I accept liars are liars and just look them in the eye. Truth is liars usually always run away when you do that, so its not like you have to keep dealing with them.
...and the pompous ones who insist they are right, they are just bullies... lonely usually. Often they have been given power and misused it, so it is taken away. Then they act out because they are lost without it.
The poor grammar thing used to bug me too, until I began publishing a newspaper and old biddies would ring me each week without fail, to tell me I had mispelt one word after preparing and printing 28 pages with barely any sleep and constant demands. I will never complain about a printing error again...
I love people... their idiosyncracies... their humanity or lack of it... the way they communicate... or what they will defend...I like looking at the way they treat their mothers and then how they treat a dog or a noisy kid... things like that amuse and interest me.
I think my pet hates would probably be way too simple... pathetic probably.
It bugs me when my daughter takes stuff off my desk and then loses it. (My stapler has been missing for 2 weeks now!)
It bugs me that I am always the one who has to pick up the toilet paper wrapper off the floor and put it in the bin next to the loo, and then put the open and used roll on the dispenser. I may never work that one out.
And I don't like mobbing behaviours... when folks gang up on things or people. Whenever I see that, I distrust their issue, because I figure if it was valid it would have made a difference when the first person said it.  I don't support mobbing. I figure 50 people could tell me my house was on fire, but I wouldn't turn the hose on until I smelt smoke.