To be honest, I feel like the whole demons-aren't-evil-shit really doesn't work in taizai. Why, you ask? Well for starters, almost everything related to the demons in this manga has been related to destruction. It wasn't just about morals either. It was almost a science. What did Meliodas do in demon mode in Vaizel? Attack everyone and everything in sight (except for Elizabeth) What happens when you get demon Blood injected to you? You either explode or turn into a mindless killing machine unless you have extreme confidence. What was the 10 commandments' first course of action? Visibly enjoying their killing spree. Apart from the whole demon children thing, and Meliodas being a good guy(who still went berserk several times) Nakaba has done a very poor job at making me sympathise with the demons.
Did Meliodas really attack everybody on sight he got his very important sword back (did he care about Guila no she was the enemy)
then he saved Elizabeth who ask him 2 when he attack Guila & Jericho,
Meliodas went out of his way to avoid sending Ban flying if you look at the panel when Meliodas charge through Guila & Jericho he had his hands in a fist
then when Ban got in his way he change is hand into a chop
then he went towards Elizabeth & made sure she was ok
& he then saved King who was getting whooped at the time by Helbram
& from this interaction with Ban & Elizabeth he did it all on purpose he knew what he was doing
Now as for the other Demons Zeldris went out of his way 2 save/punish the entire Vampire clan because he loved one of them when he was order 2 & could of simply killed them all except for Gelda especially since his power level is at least 2x all of them combined
The Ten Commandments/ The Demon Clan are piss that the Goddess, the Fairy, the Giants & THE HUMANS were responsible in them getting sealed Zeldris made it clear this is about vengeance.
When has Meliodas ever gone Berserk you can't be talking about at Camelot right?
As for taking in Demon Blood we don't what happen if you take in Goddess blood so I can't really argue about the exploding thing but even in real life if you take in blood that don't sync with your own you die. But as far as turning into a mindless monster if you are not talking about what Hendrickson did 2 the New Generation I disagree have Jericho really changed since the first 100 chapter & the second 100 chapter she is the exact same the Demon Blood didn't change her personality.
Now do it help that most Demons favorite food is souls no it don't but that don't change the fact that if there's new leadership between the Demons & Goddess that there can't be peace between clans.
Are the Demons goody 2 shoes HELL NO but nobody is in this series everybody is at least gray what about the humans who rip off the fairys wings & then sold a dead fairy body multiple times & it's the humans who are most likely the cause for Gloxiana sister transformation. Obviously the Demons but what about the Goddess who really caused the Holy War when there was peace/ a truce between the clans. What about the Giants who sole purpose in life is 2 fight.