I haven’t heard an argument against them that isn’t based in hatred and bigotry. It’s a flag that signifies the acceptance of people being able to express love to each other in more ways than one. The flag, while generally rooted in definitions surrounding sexuality, is not a symbol of sex. The flag isn’t encouraging sexuality whatsoever, it signifies a culture of acceptance of people regardless of how they think or feel. Fighting to have it removed is just fighting against accepting people as they are, which is a quality that is also common to bigots, racists, homophobes, and Nazis. It isn’t okay to just start calling people names because of an opinion, but I can see how the conclusion could be made as a knee-jerk reaction to someone wanting to ban the flag.
You seriously underestimate the stupidity of 80% of windows users. They could put multiple warnings and people would still click past them without reading then bitch to their IT team when they break something.