Diddy's Lawyers Claim Voyeurism Doesn't Count as Prostitution

Diddy's hearing on his motion to get the Mann Act charges thrown out started just a short time ago ... and, his lawyers are taking their argument from legal motions to real life -- firing off in a New York City courtroom.

The rapper's legal team -- led by Marc Agnifilo -- kicked off their argument by repeating to the judge what they previously stated in legal papers ... prostitution means one person paying to have sex with another person. They insist it doesn't refer to someone who pays to watch two people have sex, like Diddy did.

However, prosecutors responded by pointing out Diddy wasn't just going somewhere and sitting in a booth to watch two people get it on ... they say he reimbursed his ex-girlfriends for arranging the sexual encounters and derived sexual gratification himself from watching.

Prosecutors also add the charges can't come down to a free speech issue -- in a pornography sense -- because not every sexual encounter was filmed.

Diddy's lawyers fired back by arguing it was filmed most of the time. They also say Diddy was engaged in amateur pornography, which they say isn't a crime.

Diddy's team attacked the foundation of the Mann Act too ... calling it an old, racist law judges have expressed outrage about over the last 100 years.

As you know ... Diddy's lawyers, his family and prosecutors all rolled up to the courtroom shortly before the hearing to find out if the 2 Mann Act convictions will be tossed or if he will get another trial on them.