Sense of humor varies from person to person. Many years ago a movie was made to deter teens from smoking marijuana. It was called "Refer Madness". The movie was not a comedy and yet today it's considered cult comedy classic!
In other instances sometimes people mistake dead seriousness with sarcasm. They may believe the author truly does not believe what he/she has written and it was intended to be a witty piece.
Lastly as JThomp42 stated they may have marked it funny because they totally disagreed with everything you said.
Regardless of the fact every comment, vote up, or rating you get improves your over score for that hub.
A vote down would be worse than getting a "funny" rating.