It doesn't destroy bread, it just makes it disgusting... one could say it may even turn into an acquired taste, specially if you are into bread flavored chewing gum.
Microwaves don't cook food, they cause the food's atoms to speed up causing them to heat up and boil themselves, it's entirely different to a stove, reason why it also has the potential to cause cancer to people with a pre-disposition to getting it. Some stuff HAVE to be heated normally otherwise the bonds between the atoms don't break down properly after heating, ruining the food (eg: fluffy breads).