Weren't they planning on herding everyone to the roof and blowing it up?
The plan was to do that to cover their getaway. Herd the hostages up to the roof, nominally to stop snipers while they got in a helicopter. Then flow it all up. By the time they sorted the body parts and realized they weren't there, they would be gone and safe by a different route.
This is also why getting the detonators back was so important. Without them, they couldn't blow the roof.
Oh nononono that's totally unacceptable. First of all, John McClane is the epitome of toxic masculinity — he smokes, he swears, he shoots guns, and he clearly cannot stop himself from stalking his ex-wife against her clear wishes to be left alone.
Second, he's also a racist, who, in a several acts of clear and utter police brutality murders a calm and well-mannered German gentleman (played by a British actor) and his merry band of European immigrants who are merely trying to settle a dispute between themselves and a Japanese megacorporation in order to improve their local economy and feed starving children at home.
If you're watching this movie in 2023, you're definitely an alt-right terrorist and you belong on a watchlist.