Justin Bieber's bodyguards got physical with paparazzi trying to shoot his arrival at a yacht party in Miami -- prompting Justin to get a little whiny ... pleading about how difficult his life has become.

Watch the vid ... Justin was about to kick off his booze-filled 4th of July bash when one of his bodyguards -- who's already been arrested in Miami -- threw a hard forearm into the chest of a pap running up to the scene.

To his credit, Justin tried to calm the situation from the backseat of his SUV limo -- asking the paps to just back up 10 feet, but when they didn't he went into woe-is-me mode.

You gotta see Justin beg a female photog, "This is so ridiculous. Look what happens in my life."

And then he got on the yacht and partied without a worry in the world.