Robert F. Kennedy Jr. is in the middle of a heated debate around the viral photo of him walking barefoot on an airplane, and his response proves he's keeping 10 toes down on his stance on this issue.

The presidential candidate sent a video response to TMZ -- after seeing the controversy bubble up in our newsroom -- and he tells us it's "inexcusable" for politicians to go barefoot on an airplane and promises to never repeat the same foot faux pas.

Ya gotta see RFK Jr.'s video ... once he finishes his "apology" the camera pans away to show the naked truth -- and while he's not midflight in the video, he is sitting in an airport terminal.