No. They were not children. They were young adults but by no means were they children. You're just piling on excuses for them at this point with that argument. And I don't have unrealistic expectations. If you are part of a small society, who largely contains members of the Auror (which is basically, what, magical MI6? So magical James Bonds?), then I expect you to keep a level head regardless of your emotion. I'm holding him accountable to the position he was in. And, clearly, he was unfit for that position as demonstrated by how he acted. Which, to be fair, is Albus Dumbledore's fault for putting trust in what are essentially college students. You will never convince me that there weren't more qualified Wizards out there who weren't in their early twenties. But, again, that circles back around to flaws on Albus Dumbledore more so than Sirius Black.
If Sirius Black loved Harry Potter with all of his heart, he wouldn't have left him alone. Sirius Black loved James Potter with all of his heart and thus was fixated more on avenging him than taking care of the infant. You know who truly loved Harry Potter? Molly Weasley. Rubeus Hagrid. Minerva McGonagall.
And, really, there is no reason to be offended over a literary debate.