Nobody is their best selves all the time. We all have days, weeks, and even whole years where our emotional capacity is severely limited, and with it, our ability to be as present and openly loving as we'd like to be. It's completely natural to have lows, and behaviors we look back on and cringe at, but there's a big difference between having grace towards everyone's humanity, and completely excusing a**hole behavior.
Sadly, there are many ways in which American culture gives way more leeway to straight-up a**hole behavior than vulnerability or earnest missteps. The reasons for that vary widely, but the litany of commonly accepted excuses for a**hole behavior certainly contribute to the problem.
“That’s just how they are.”
One of the biggest enablers for tantrum throwing, bullying, etc is that they get treated with kid gloves to avoid dealing with them.