The police can do a lot of things without a warrant that you and I shouldn't and often can't do. For instance: they can pull your car over and then shine a flashlight through the windows to inspect what's visible in plain sight in the passenger compartment.
They can pull your car over with cause, yes. This is something we cannot do. However, it's not illegal for you or I to view the contents of someone's car, even with a flashlight. If it's in plain sight, it's perfectly legal.
There's a lot that maybe we shouldn't do but is completely legal anyway.
I doubt this was fully legal. It's been repeatedly upheld that a private home has a reasonable expectation of privacy (this is a legal, not lay distinction) - which is to say that recording inside a private home, even without trespass, can be illegal.
Something being in plain sight is not a sufficient condition for legally photographing it. You cannot, for example, point a camera into your neighbor's bedroom, photograph the results, and distribute it on the internet, even if, say, the camera was on public sidewalks.
Does it matter that they may go to jail when you've had your ass kicked or worse[1] (personal friend). Crazy is everywhere and you don't really know when it's going to pop up.
While your friend's death is tragic, like you said crazy is everywhere and you don't really know when it's going to pop up. From the sounds of it, your friend did nothing to purposefully agitate his attacker and had no way of predicting the possible outcome. From that point of view, you may as well argue that you shouldn't merge lanes on the highway if someone is in sight of you, because that could set them off.
Yeah, it's possible to predict a poor outcome from something like this. It's possible to predict a poor outcome from anything. It all depends on how much fear you want to live with.
