i saw my step D microwaving it when he first got it. i thought it was stupid and dangerous.
It's ok, but it's not the best way to serve warm sake. Warm sake has a great flavour, and the Japanese will often put it in a proper sake jar, then submerge the jar in hot water to get it to the desired temperature. This actually takes less time than putting it in the microwave and is a better way to release the flavour. You can serve it cold too, but it's better sipped warm in my opinion.
Of course it is okay to microwave sake, so long as you don't over heat it.
In fact, it's quite normal to microwave sake. It's easily warmed by placing it in a saucepan of hot water or in a microwave. Warmed sake should be just above body temperature, about 100-104 degrees Fahrenheit.
Why did you think it was stupid and dangerous?
Yes you can microwave sake.