Yes, the witnesses are more likely to be afraid when they have witnessed a hate crime. I believe this is because that the perpetrators of this crimes are more likely to take revenge on those who might send them to prison. If you are able to do one hate crime, you can do another without a problem.
I believe that witnesses are less likely to forward in hate crime cases as opposed to other cases in which the crime is objective right or wrong. While hate crimes are wrong, I think some people are wary of stepping forward and putting themselves out there to take a side in a social issue that could result in others adopting a negative opinion of them.
No, witnesses are not less likely to step forward in hate crime cases. In many ways, they should be more willing. They should come forward in order to create justice. They should not keep their voices silent. If they have seen something that would qualify as a hate crime, they must come forward.
There are factors in all types of crimes that make people unlikely to come forward as witnesses. Fear is a common deterrent in all types of crimes so it is hard to call people less likely to come forward in the case of any type of crime. People who witness a hate crime are neither more likely or less likely to come forward. It depends more on the witness than the crime.