There will always be something, sadly. I have a negative opinion of people who like pineapple on Pizza. It's what we as humans do. Would only take someone more charismatic than myself and someone who is able to get the ear of the masses and before you know it we'll be rounding up people who like Hawaiian pizzas in the streets.
I, probably in a minority, don't even think it's completely fair to blame religion. Practically all religious people I've met have been some of the loveliest human beings I've met and have values I respect. Doesn't matter if they follow Christianity, Catholicism, Judaism, Islam, Sikh or any other fringe religion I've never actually met an out-and-out arse who follows religion in the wild.
The issue is and will always be extremism. It's like tarring all travelling English football fans as hooligans because there is a small and very loud minority. 99.9% of the football fans just want to support their team and watch sport. It's that 0.01% royally screwing it up.
Religion is just the tool the controllers use. "in the name of religion". But I do wonder if there would be less control of people didn't believe in after lives. After all, if you do X and get a life of paradise, and you truly believe it, it's a powerful tool.
Obviously there'd still be wars, but IMO, there'd be less.