Blas

Now, quit being so blasé about this.

She's completely blasé about the dangers of smoking.

Admittedly, they found the idea of a police state blasé.

What's the difference between passé and blasé?

She didn't like the blasé way he dismissed her suspicions.

I know what it means to have a temper. You’ve seen what I'm like when I lose control. But even at my worst, I'd never willingly kill someone! And if I did, I know I'd feel some serious remorse for it. Even if I'd felt vindicated in the moment, once I calmed down, I'd regret my actions. I would never be so blasé or flippant about taking a human life, and neither should you!