1.) Self defense, but there's a whole thread devoted to this so I'm not too worried about this point :P
2.) Yeah I read about that, it was tragic :(. However, the dispatcher didn't tell them that the gun was a toy (even though the dispatcher had the info) and when the cops told the kid to drop the gun he actually pointed it at them. In a world where gangs intitate members at twelve and thirteen and these kids go on to kill people, police actually have to respond these way to armed kids in the inner city.
3.) What happened there? I haven't heard about this one yet.
4.) That was a movie where guys did stupid things while pretending to be cops. It wasn't a cop movie :P
But yeah, I pretty much look at them them the same still. They have a magnifying glass to their actions right now because of Ferguson and everyone's out to get them, but when there are people who intentionally try to kill police on principle they tend to not give the other side time to kill them first. Especially when there's an entire method of suicide dedicated specifically to killing as many police officers as you can before you turn the gun on yourself (google "suicide by cop").
That being said, there are definately bad cops out there. Nobody can deny that. There are bad cops who work side by side my with my own father and let me tell you that these guys cause the good cops HUGE headaches. But regardless of whether you're a good cop or a bad cop, you get disrespected or even shot at all the same.