If you look back on any major oppressive event throughout history you will notice a common element:

Justification. Whether the acceptance is express or tacit, it often becomes so through it's justification.

Unless you are a misanthropist that believes people are inherently evil, there has to be a reason large groups of people can unabashedly violate the rights of their fellow humans.

Did people randomly decide to take on slaves or were people convinced it was okay? Did the Holocaust happen because Germans are inherently antisemitic?

How do such atrocities become accepted by the population at large?

This is done through propaganda. If you hammer into people's heads that black people are wild uncivilized animals then its easy to justify treating them that way. If you convince people that Jews are evil and a threat to your existence then it is easy to support their eradication.

Do you think the average slave owner/German thought they were a bad person?

The bottom line is simple. Just like people cling to religion to inform them of why we exist, there is also a need to understand why bad things happen to us. If you can thoroughly convince someone that there is a certain reason they have suffered then the contempt that follows is only natural.

So when I see Feminists saying things like "KillAllMen", I am not offended because I take their threats seriously. When I witness the ever growing vilification of men as oppressors and conversations of "toxic masculinity", I am not offended because I think they are talking about me specifically.

No. I'm offended because it is intellectually dishonest to pretend to correct a phenomena when you haven't dug deep enough to understand the root cause. They literally came across the first explanation that felt good and ran with it. They forget that Patriarchy is a theory and should be treated as such until proven.

What they don't realize is they've fallen into the same trap that the oppressors of the past fell into. They've painted men as the sole source of their suffering and allowed confirmation bias to cloud their objectivity. Today KillAllMen is a harmless catch-phrase. Tomorrow internment camps. After all if one M&M is poisoned it is only logical to discard the entire bag.

I am not an anti-feminist. It would be intellectually dishonest of us to argue that some aspects of society aren't androcentric. There is no use in either side claiming overall victimhood status at the expense of the other. However I will NOT support a movement that so clearly hasn't learned a damned thing from history and is willing to recreate the same mistakes of the past at the expense of men.