'busting someone' can mean exposing or revealing someone's activities that were considered inappropriate or unacceptable. Before they were 'busted', no one knew about what they were doing, but now you 'busting' them has revealed it. A 'creep' is a negative description of someone whose behaviour is strange/weird/socially or morally unacceptable. "I do support you busting the creep." thus means I support you exposing or revealing what this weird/slimy person has done.

I'm a native speaker from the states, and I've never heard this expression before, do you have more context?