The National Organization for Marriage is a group which travels across the country, condemning homosexuality and advocating against new laws allowing gay marriage. What type of movement are they participating in?

Resistance

Explanation:

Homosexuality is the romantic, sexual attraction between the same sex and it also gives a person a sense of identity-based on these attractions. Historically homosexuality is a subject of resistance to the conservative and orthodox groups who rejected the sexual behavior of homosexual as unnatural, declaring it a sin and later mental disorder. Modern society accepts homosexuals as normal people but there is still resistance from the conservative section of society.