"I choose to ignore this entire part of the story because it doesn't fit my view." Okay dude that's fine it still makes him a prick we are also never given a reason to fucking care about Deryl your kidself just goes and helps someone who was a cunt for no reason. I didn't forget anything the dead moms is the only reason the MC does anything with Deryl and that's flimsy reasoning.
We are given plenty of damn reasons to 'like' or 'care' about Deryl, you're just ignoring them.
To put it simple, when a player first gets into the game they are introduced to multiple characters and Deryl is obviously one of them.
Liz is a character whom the MC is setup to have been avoiding as of late which sets the tone of tension between the two (I believe MC asked her out or whatever prior to the game start).
Deryl isn't like this whatsoever and is quite friendly towards the MC and continues to be just like this throughout the game up to a certain point.
Your reasoning for ignoring the blatant and obvious reason for liking him is quite apparent. I ignored the past because it's not relevant and nor will it ever be...because its the past. We are introduced to him as friends and the past is nothing more than backstory for how their friendship started.
Was kid Deryl a dick? Sure. Although we cannot forget the obvious that Deryl just recently lost his mother and before you say some shit about "The MC isn't acting like him" every human reacts differently to death and Deryl is lashing out as his response and acting like a dick. I won't fault a child for not being able to handle shit like that properly.
The MC also has the choice to egg Deryl on and amp up Deryl's antics so I won't put MC on a high standard of 'good' and not being a 'dick' either...although both are kids and kids have a habit of being dicks.
It's also kinda funny you actually think the mom thing is the 'only' reason whatsoever for their friendship. It's very clear that MC helping Deryl during that fight with his dad had impact and it cannot be ignored. (Oh and lets not forget the blatant child abuse that happened to Deryl and his brother due to his mother's death...I believe that's what caused his dad to go off the deep end and it also attributes to Deryl's dickish behavior).
But you know...go on and continue your blind hatred of a character simply because you can't pull yer head out of your ass because "PaSt DeRyL bAd"