Hello, I want to know AITA for being too strict with my paladin. Me (Dungeon Master) and my d&d group who have all been playing together for the past 4 months on Roll20. We recently had something happen and the group thought it would be a good idea to reboot our game but a few years in the future. The issue arose when my closest friend wanted to play a Paladin. I naturally hate paladins because I've only had bad experiences with players who have played the lawful stupid stereotype. Either way I was willing to give this a try. Before we start I want to sit down in a VC with Paladin and discuss the oath that he has chosen since it is a big part of the Paladins choices in the game. He ended up choosing a paladin who chose the oath of the ancients. For reference the tenets

• Kindle the Light. Through your acts of mercy, kindness, and forgiveness, kindle the light of hope in the world, beating back despair.
• Shelter the Light. Where there is good, beauty, love, and laughter in the world, stand against the wickedness that would swallow it. Where life flourishes, stand against the forces that would render it barren.
• Preserve Your Own Light. Delight in song and laughter, in beauty and art. If you allow the light to die in your own heart, you can't preserve it in the world.
• Be the Light. Be a glorious beacon for all who live in despair. Let the light of your joy and courage shine forth in all your deeds.

The problem was when we were starting to discuss what constituted breaking his Oath. Paladin's backstory is that he lived in a village and a group of adventurers warned his village of an impending attack. The adventurers while helping the village would turn on them and kill the villagers only leaving Paladin. Paladin would then vow vengeance on the adventures and would be adopted by an archfey and take up the oath of ancients paladin.
I would then ask why he doesn't just take up vengeance paladin since that is what his character seems to want. He then would say how "Vengeance paladins are overplayed' and how his goals still aligns with his tenants. I disagree and say if he means to kill them then they do not especially the first tenants. "Through your acts of mercy, kindness, and forgiveness, kindle the light of hope in the world, beating back despair." We then talk a little more and I actually get him to specify that he wants to just expose this group and will only will them if he and the party's lives are in danger from them. Side note I did say he does not have to spare every evil person we run into if they are hurting you and the party you can kill them. I did say after that if they do surrender to him (they drop armor, weapons, and other harmful equipment) that if he just up and kills them that he would be breaking his oath. This turned into a HUGE argument about how Paladin believes that he knows these peoples and if he did anything other than killing them that they would just be free to roam around and commit more crimes and hurt more people. I told him that he could turn them into the Guards in a local city since he would be exposing their crimes this would make that even easier for him. Paladin's argument is that in the second tenant that "stand against the forces that would render it barren" would trump the first and he should be allowed to kill them. I said it not a matter of what trumps what, A paladin has to live by all his tenants and if he does not he just becomes an oathbreaker. We argued forever and this even has our party split on if this is or isn't oathbreaking. I put my foot down and said fuck it and just told him not to play the character and pick something else. Now I feel like things are weird between us and I want to know AITA for this situation.

Update: I talked to paladin and admitted thanks to most of your comments that I was a little to harsh on him and the character he was making due to my bias. We are still going to playing together on our regular game, but Paladin said he was a little peeved but this never really changed his opinion on me but the apology goes a long way. I did mention this current game is 4 months old but me and him have been playing for almost 2 years and he previously knew about my hate for the class, but I was how we ended our convo that made me ask myself and reddit AITA. I sent him the post and he laughed cause he just thought this was one of our many disagreements and didn't think that I actually felt like an Ass. I did and posted it but fortunately for me something like this wasn't enough to stop me and Paladin (Now Barbarian) from playing. Also small tangent for me yes it is my game as a DM but I truly believe that the game we play is all of our game and my PC's opinions/feelings are just as important. I do every now and then step in and final say something but with this group I feel truly lucky because that seems to be few and far in between. Either way thank you all for your comments I greatly appreciate everyones opinions.