I also remember when they fucked up the metal category and Metallica lost with the black album against that flute playing douche. 
... yeah... that's pretty fucked....
Now now.... let's look at that scientifically:
Heavy Metal Instruments Metallica Jethro Tull drums, check drums, check
guitars NOT heavy, nor metal ditto
keyboards... not much, and they're yeah, some, what about it?
mostly plastic
flute... heavy, metal instrument...
...[crickets]
...And so, Jethro Tull wins, two heavy metal instruments to one (Three if you count grand piano.)
Get over it. They're just lucky they weren't up against, say, Fleetwood Mac and the USC marching band.
Say, do they still
have Grammy Awards? I wonder when they're on...