Felt bad for De Niro's character

Many people don't deserve what they get. Hell, Arthur didn't deserve what he got before turning into the Joker. He was nice and taking good care of his mother. What gratitude does he get for it? None! Even the social worker lady didn't give two shits about him. And it was her job.

We do not clearly know that it really happend. It could be only in the Joker's mind after all. Killing his Idol to become the joker he was meant to be. On the other hand. Murray was making fun of Arthur so he was not innocent too,,,,

I don't think we are supposed to vilify Murray, at least I didn't. I think Murray subverts our expectations because we expect him to be nice onscreen and an asshole offscreen but he's pretty much the same guy. My read was that he wanted to entertain his audience but also give Arthur something out of it. Did he make fun of Arthur? Yes. But making fun of someone doesn't mean we dislike them or are bad people, it's a normal part of establishing hierarchy in social networks.

Well, you either die a hero or...oh wait...

The sole reason why Murray invites Arthur on his show and, in turn, gives Arthur exposure, is so Murray could mock him on national television and get the viewers to laugh at Arthur's expense.

Murray's producer even voices his concern to Murray, calling Arthur a "nut" and that putting Arthur on the show is a bad idea given the current rioting to which Murray replies, "I already know he's a nut. That's why we're putting him on; it's a goof."

Clearly, Murray isn't thinking about Gotham, let alone Arthur and his mental health; Murray is thinking about Murray.

Of course it doesn't warrant being murdered in front of a live studio audience, but which of Arthur's victims' actions does? Sure, an argument could be made for the men in the subway, but murder remains murder.

The point is, as far as Arthur and most people are concerned, Murray is just another selfish bully and part of the problem with society.

How do you live day to day knowing that things like this is very possible?

Well, he is crazy. You're not supposed to think he deserved what he got.

I think it was unfortunately a nice touch. It helps you to understand just how corrupt and dangerous Arthur had become without his meds. In his mind, the slightest infraction upon his fragile psych could result in someone's death. No matter how good or bad they may seem.