In order to stop the discrimination, hate crimes, employment regulations (teaching), marriage and right to life based on people's sexual orientation, gender, sexual identity - it is important to follow in the foot steps of contries that have achieved this - namely - European countries.
"Legalizing" marriage for homosexuals state by state will not solve this. Most all countries where homosexual marriage is legal started way before by adding rights for GLBT people and sexual identity rights to their constitutions. Then when they had many years of full rights as citizens for employment, teaching, living, life, etc.. passing marriage laws became really easy.
The USA should follow suit on a federal level by adding an amendment to the constitution. It is a human right to love who we love