Why are all these people invoking "5th Amendment" right?  

5th Amendment right is invoked to protect against self-incrimination

Obsy says this is a "kangaroo court" -

So, if they have nothing to hide, why would they think that testifying would incriminate themselves?

That, my friends, is what the 5th amendment is about

You can continue to make excuses that make you feel good about yourself, but you know deep down inside they are trying to protect themselves against "Self-incriminaton"... OR protecting the president

Which one do you think is more likely?