quick question: if barkley was under investigation for indecent assault, is there such a thing as a "decent" assault?
Of course not. Assault is an intentional or reckless thread of injury. Indecent assault means it was of a sexual-related injury. You don't need to call a non-sexual injury "decent," as that word connotates more than just the opposite of indecent.
then why not just say plain and simple sexual assault? if he groped the girl, why not call it as such?
Indecent is just a term that reporters use, and it has its own meaning. It's not as severe as a sexual assault, and invades a privacy interest in the body related to dignity rather than actual sex. Each state uses different terms for their crimes, it gets confusing. In the 50's, they tried to get states to adopt a model code which actually did get used in parts, but there are many parts which states haven't changed, going back as far as their formation as a state.