I've got to disagree here, and again, I'm going off of personal experience at only four companies. On the one hand, of the four companies, three were well established, and none were startups -- however, in a strike against them as far as discrimination is concerned, the they were in telecom and performed layoffs once to twice a year of about 5-10% of staff (more during 2007-2008). The only blatant cases of discrimination I witnessed were two occasions where older employees were let go due to them being close to retirement age[0].

Accusing individuals of turning a blind eye to discrimination is a pretty strong charge. An equally strong charge would be to state that some individuals go out of their way to look for discrimination where none exists and call those individuals something akin to "snowflakes". To be clear: I don't, personally, believe either of these things, but I think it's important to play Devil's Advocate from time to time.

Another possibility is that people saying "it's unbelievable" do so because they, themselves, wouldn't dream of acting in this manner or being part of a team where this kind of behavior went on. And I think some people disregard "bigotry and rampant unprofessionalism" because human nature tends toward avoiding confrontation (or risking one's job by causing a problem for an influential manager). That last bit is the worst case because it causes the problem to be sanctioned through inaction, it damages the company, its shareholders, its customers and its employees[1], which causes a feedback loop making it even harder to stand up when something unethical is witnessed.

[0] This was done because the managers thought it was the best option for everyone -- the two guys were with the company a long time, would receive a very big severance package (this company had a great severance offering) and they were preventing another few employees from being let go who were younger with families. Unfortunately, I know that in one case, the individual let go was both a high performer and had no desire to retire at retirement age. It was ugly and I nearly left the company after it happened (I only stayed because they were being bought out and the new company was taking us over -- it was as good as getting a new job as the two places didn't resemble each other on anything but paper).

[1] And I get it -- I was personally told on one occasion by my boss that he "had just spent an hour convincing our VP that I should keep my job" because I pointed out a large license violation I had discovered and wasn't aware that the person responsible for that (unintentional) licensing oversight was in the room. In the end, though, I would have done it regardless and my actions resulted in that manager being forced to work with the vendor, avoided an audit and negotiation got us pennies on the dollar to become compliant, again.