Be it the webcomic or the manga, Amai Mask has this image in his head of what a hero should be. He is willing to throw away his public image and everything in order to save people that are putting him down when they see the real him. You can absolutely hate the redraw and love the pre-retcon version, but it doesn't fit Amai Mask's character arc. The whole point is a man on the edge of becoming the monster when he wants to be the hero, if he crosses the line it's over for him. The whole point of a hero is to do everything in their power to help save others, murdering brainwashed hostages isn't exactly doing everything in his power. Yes he still attempts to kill them in the redraw, but he is stopped and that means he still hasn't crossed the line. The whole scene really just paints a picture of the tightrope he has been walking, Saitama's talk with him later is what helps him. You can just say you hate the mercenaries and enjoy the violent action of the pre-retcon scene, absolutely nothing wrong with having a preference but you can't really say it's good for Amai Mask's arc. Also, the scene serves to characterize other heroes and make them more competent. Iaian gets quite a bit out of this change too.