The problem is: It IS optional, there IS a skip button, and it's NOT dominant in the story (so far, and I hope it stays that way).
It's a flashback to the MC catching his ex cheating on him. That's it. Literally it. It's even hinted at BEFORE you even see the flashback when the MC looks at the picture of him, his ex, and his "best friend" and he then mention's something along the lines of "them rewriting the script without him" or "writing their own love story behind the scenes" or something like that. Doesn't take a genius to assume something's going on between those two. Then lo and behold, the flashback happens.
The hate's undeserved in this scenario imo as the scene accomplishes its goal which is to establish the MC's past, give you a key reason as to why he's basically trying to "become" someone else by completely changing his personality, and establish a sort of antagonist/hyper douchebag that nobody likes. Hence the whole "Lies we tell ourselves" part of the game's title as well as its constant references to "wearing masks." His personality change is just a mask he wears due to the betrayal.