While law alone is never enough to change social attitudes, law does make a statement that can make people think about what is the social norm and along with other factors can help to change attitudes. Hate crime laws make the clear statement that bigotry and discrimination is not tolerated, and are one in a number of ways that social attitudes have begun to change.
No, I do not think that hate crimes have or will change social attitudes. Most people that have hatred for another race, religion or sexual orientation do not commit violent acts, so they have no incentive to change their views because of hate crime laws. And for the people who do commit violent acts against other groups, they have so much hatred that a stiffer penalty won't stop them.