I believe it has something to do with the stereotyping system that exists in the brains of most higher organisms.

For example, my cat is deathly afraid of my belt. She has never been threatened or struck with it so I can only assume that she thinks it's a snake. She has never seen a snake but somewhere in her instincts snakes and snake-like things are stereotyped as being dangerous.

In humans, social stereotypes have a strong learned component. Most software developers have encountered sales, marketing and management people that have barely enough technical savvy to create problems for no good reason and more than enough social ability and/or leverage to force us into fixing the problem they caused. These people are usually groomed and well dressed.

When someone groomed and well dressed enters a software developer's workspace, without knowing who they are, what they know and why they're there, the developer's mind will search for a stereotype to fit the person. This process is involuntary and automatic unless they make a deliberate effort to not apply stereotypes. The best fit stereotype for this new person is that of the sales/marketing/manager above. The developer will harden themselves into a defensive mental stance by keeping all answers to inevitable questions vague and withholding genuine trust and respect while projecting false respect out of professional politeness.

This new person may be another developer, one with comparable skills and credentials to that of the more hastily groomed developer. This new developer may just like the way they look in a suit but to the old developer they look like a snake in the same way a belt looks like a snake to my cat.

Stereotypes take effort and exposure to break. That effort needs to come from both sides and the person projecting wrongfully negative stereotypes needs to stick around and interact long enough for the exposure to sink in. When someone is wrongfully prejudged on race, gender or clothing and they immediately respond by immediately turning on their heels to report the offense and apply the biggest and most powerful tools of policy, law and social shaming they can get their hands on, they just add more negative aspects to the existing stereotype. Now that stereotype includes 'easy to offend' and 'severe consequences if offended' for everyone within earshot, not just the person fired, jailed or shamed. The next person who triggers that stereotype will have that much more of a barrier between them and the people that witnessed 'the incident'.

It's certainly unfair having to clean up stereotypes left by people that have long since come and gone. The fact is, however, they are no longer here but their mess is; someone will need to clean it up and that someone is probably going to be a person deeply affected by it.