Little People of America -- We Are PEOPLE ... Not Bowling Balls

Little people are NOT objects to be greased up and hurled down a bowling lane for the sick enjoyment of an audience -- so says the Little People of America, which tells TMZ, Zac Brown's "midget bowling" is a "direct insult" to little people everywhere.

You'll recall ... TMZ posted footage of country singer Zac Brown going "midget bowling" at a motorcycle rally in South Dakota last weekend -- sliding a little person named Short Sleeve Sampson down a greasy ramp ... and into bowling pins (he got a strike).

But a rep for Little People of America -- the country's biggest non-profit for people with dwarfism -- tells TMZ, "Little People of America does not endorse any activity in which a person of short stature is used as an object rather than regarded as a competitor, in a 'sporting event.'"

The rep adds, "We believe that such practices are a direct insult to the equality of people with dwarfism, grounded in a respect for basic human dignity."

But tell that to Short Sleeve Sampson -- he called in to TMZ Live earlier this week ... insisting there's NOTHING wrong with a little "midget bowling" every now and then.