People who have not shared the same experiences always have a hard time fully appreciating how the other feels. Having been a hippie in the 60's and 70's I had my share of run-ins with the police and the majority of them were unwarranted, so I think I have an idea of what black people feel about the police, but I readily admit I can't really appreciate it fully. I've no doubt at all that black people are disproportionately hassled by cops, and there's no excuse for it.
Quantifying the problem is impossible, because I also have no doubt there are occasions when the person complaining has no reason to,(This is a characteristic of people in general; not just black people) but it's certainly enough of a problem that it allows for some segment of the population to raise false complaints and be believed at face value. This is the cops fault though, because if there weren't the number of legitimate complaints there are, people would be far less inclined to immediately believe the false ones.
Unfortunately, "the cops" are not one person who can be blamed and so there is a possibility that one who has not had a track record of improper behavior can get, unfairly, caught up in a mess, but this is just another reason why all cops should get behind whatever it takes to solve or at least greatly reduce the problem and not immediately go on the defensive when the subject comes up.
I think the chest cam is a good idea, and while I can imagine why even a decent cop might be wary of it, it the long run it will help the decent cops defend themselves against the false complaints, and help weed out or at least restrain the bad ones. It's not a perfect solution because these cams aren't perfect. It's not tough to imagine a bad cop coming up with some way to dismantle the camera or a way for the camera to simply break or stop working. I'm pretty sure that if an incident arose that wasn't caught by the camera because it wasn't working, the immediate assumption would be that the cop deliberately broke it. I don't know any way around this though so I guess we'll just have to hope it doesn't happen often, and insist that the justice system, at least, doesn't consider a malfunctioning camera to be proof of a cop's guilt.
I also understand your co-workers thinking (and why it bothered you). The media does hype a lot of topics, and not just this one. I don't think you can fault anyone for not trusting the media to report matters fairly when we see examples of unfair reporting on a daily basis. This isn't a right/left thing because a large majority of Americans don't trust the media. It's also fairly natural for people to believe the media is hyping things that either they themselves don't believe or don't wish to believe.
AS for the president's commenting on these incidents, I do have a problem when his comments assume the outcome of an ongoing investigation. Jumping to conclusions is another human trait, and a lot of people think they know what happened in Ferguson based on what they have read or heard. These people may all be right, but what they all have heard or read is not all the evidence that exists and that evidence has not been considered fully within the judicial system. It's fine for me or you to have an opinion and voice it whenever and wherever we please, but we are not the president of the United States. It is entirely inappropriate for him to render his opinion, in any way, on a matter that is still the subject of an ongoing investigation; or had not been adjudicated. Speaking of the broader issues is not only fine, it's a good idea but he needs to stay clear of specific cases that have not yet had a formal resolution.
As for the trends relative to police killings there's another thread in this forum that address the issue in some detail so I won't repeat anything I've written there. Suffice it to say that there are a lot of understandably strong emotions concerning these incidents, and these emotions can distort the overall picture. The stats have to be confirmed. Within the other thread there’s at least one example of an article with a single word or two misrepresented certain numbers. They also have to be looked at in context. When something is horrible and very wrong, we don’t want to (nor should we) accept even one incident, but horrible things happen all the time and the measure of their significance of a trend is in relation to other numbers.
Killing by cops may indeed be on the rise, and so might the number of killing by cops that involve innocent people, but both incidents are likely to be with us for a very long time and while this doesn’t mean we shouldn't do whatever we can to reduce them, or, in the case of the latter, eliminate them altogether if possible, the increase in their number needs to be statistically meaningful if we are to label it an alarming and dangerous trend. I have zero doubt that cops kill innocent people every year, and I’m fairly sure some of those innocents (whether they are black or white) were actually murdered by cops, but it’s hard for me to imagine why these numbers would be increasing significantly. Not to say they are not but I think there is more oversight of police departments today than ever before, and society’s tolerance for rogue’s cops certainly hasn’t increased. If there has been a significant increase in cop killings and murders, there should be a reason, but it just doesn’t seem like it could be one that might be considered obvious.