Why do some people ume that everyone who votes against gay marriage is a bigot?

My home state recently voted against gay marriage, this lead to everyone there being labeled as ignorant bigots by several newspapers. Gay marriage is an issue which has been addressed by a referendum vote in 31 states and has been rejected in all 31 referendum votes. The shear number of people who have voted against gay marriage is enormous and I personally believe that there must be another reason besides bigotry which causes people to vote against gay marriage. Isn't it possible that these people are just concerned citizens who are nervous about changing the definition of marriage?