I started re-reading Halo Glasslands the other day and I noticed that Mendez is an incredible hypocrite. He hates Halsey for her involvement in the Spartan-II program and thinks she's some witch who hates humans. Granted, Halsey, at first, didn't really care whether her Spartans lived or died. But as the war with the Covenant started and dragged on, she started trying to do what she could for the human race. Mendez, however, believed that he'd been absolved of his sins in training the Spartan-IIs instead of reporting Halsey. But he's far from absolved, and he's just as much to blame for every Spartan-II who died.
Then there's the Spartan-III's, each of whom he trained personally. It's not bad enough that he trained another batch of Spartans after the II's were 'discontinued,' but he trained the Spartan-III's knowing that their rate of survival was literally 0%. Sure, he tried to save the newest III's on Onyx as the Onyx Sentinels started attacking, but the fact still remains that he knowingly and willingly trained each Spartan-III knowing that every one of them might be dead months later. The fact that Tom, Lucy, Ash, Mark, and Olivia are still alive is nothing short of a miracle. Then there's also the fact that each Spartan-III is given drugs that alter key regions in the frontal lobe, increasing aggression. And if they don't take another couple drugs, they'll go into an uncontrollable aggressive state, though Mendez didn't have a say more than likely on the drugs that were administered, he could have spoken against their usage.
Now that I've stated my reasoning, I look forward to hearing what others have to say. Please keep the hate to a minimum. I didn't make this blog to hate on Mendez. Although I do actually hate him, that was not the intent of this topic.