OP, ignore most of these comments. LR's culture is such that even when you present a problem most other "runners" would be sympathetic of, they use LR's anonymity to bash you.
You just need to get creative. Next time, let the old, whiny foagy have your treadmill. As soon as he starts going, jump on back and start running behind him. Make sure your hot, moist breath is brazing his neck. He'll be confused and yelling at you to get off 'his' treadmill, but he'll have no choice but to keep running because you're blocking his exit to the back.
Reach around him and increase the pace to 6:30. He'll be screaming at this point because he can't take this pace for more than a few seconds, yet he can't get off the treadmill because you're blocking it! Keep your striding strong. Just when you detect he's about to fail and collapse, split your legs and jump to the outside of the belt such that you're stradling the moving treadmill belt. He'll fall and be whipped under you and out the back of the treadmill, crashing violently into the weight rack.
He will have learned his lesson, and all the spectators will have also learned not to mess with you or your treadmill. You've proved that your not only superior as a runner but superior as a man, and you therefore deserve this equipment more than he does. You may have to do this several times to spread your message, but it's good training anyway. This should leave you with a feeling of pride and satisfaction in your heart.