Okay genuine question that requires some context: 

My supervisor and I are quite good friends. However there are reoccurring instances where I find myself disagreeing with what has occurred. 

For example, my supervisor has been leaving work during busy days to deal with personal issues that occurs. This was fine as a one-time thing, even a second-time thing,  however this began to occur repeatedly. It meant I had to cover their work and mine. I addressed this eventually after bottling my frustrations for so long and the situation somewhat resolved.

I have now noticed that each time I work with my supervisor, his mates come over and strike up a conversation with him. Now I’m normally pretty chill about all that, I don’t mind a good yarn. However these can last for a long time...I’m talking like 30-45 minutes. This occurs one or twice during the day. 

Today his mates approached him and talked with him for about two hours - with him doing a task here and there if he needs to (e.g. me being out back and a client appears).  This obviously frustrated me as I’m picking up that workload again while they chat.

I disclosed this with my supervisor who immediately began defending himself, stating that he wouldn’t apologise for that and argued that it doesn’t occur regularly...which it does. This led to a shutdown in the conversation as I didn’t want to engage with someone who was on the defensive, and therefore not willing to take on opposing perspectives.

I later engaged with him and said I didn’t like the conversation and we talked briefly...but he still stood by his point and said he wouldn’t apologise for it. 

We’re doing okay now but AITA for criticising him? 