1.) Let me put it to you simply. You have to prove personal bias in a hate crime case through court proceedings. Effectively if it becomes the nature of the trial to prove that he committed a hate crime, crime motivated by personal bias, then it becomes the nature of the trial to prove the ideology and opinions of the person. In order to prove that you need to understand the thoughts and opinions of the perpetrator.
2.)The illegal action of a the crime is on trial yes, but having a hate crime charge further suggests that the motivation based on the perpetrators ideology is illegal more so then just the act itself. In a sense it's illegal to attack some one, and it's illegal to be motivated by your own personal bias in the action of attacking the individual. This is how it is a thought crime. Your personal bias gets put on trial, not to simply discuss the motivation to prove you intentionally harmed the individual, but that the fact that your motivation of being biased was also illegal as well.
3.)With that being said it violates the 14th amendment because it protects a certain group of victims more so on the basis of motivation then it does to others. Effectively I could be shot by a crazy white guy who is biased towards blacks, but if a black guy is shot by a white guy with the white guy showing a bias towards blacks the black guy is now protected more favorably under the federal government, which is a contradiction towards the 14th amendment of the equal protection clause.
4.)I know I know your going to tell me I'm wrong, but the fact still remains the minute you charge someone with a hate crime, the persons political or religious beliefs and opinions become the scope of the trial, this is how hate crime legislation is actually thought crime legislation.