If you are saying I can choose to be in a relationship or not, then yes, that IS a choice I have. However, I do not choose how I feel about someone. I would very much like to fall in love and be in a relationship with someone of the same sex some day. Are you telling me I shouldn't?
Yes. I would certainly not try to legally prevent you from forming that relationship, but I am also unwilling to have my tax dollars used to endorse such a relationship as "marriage."