In Zero Gravity, whatever the Arks of the Cosmos pick up shoots off after a while and explodes. In the scene where the Babylon Rogues find an Ark (technically the first cutscene) he ends up picking up Wave and Storm. Shouldn't they have blew up too?
But, at the same time, it might just be that it doesn't cause people to explode. Besides, on Mobius Strip, you aren't the one who activates any of the Gravity Actions which affect you, and yet you don't blow up. Instead, Master Core: ABIS picks you up using Gravity Dive. If we were going by the same logic as the first trooper was saying, then shouldn't Sonic and co. also get blown up?
Sonic Riders makes it so Sonic's board is many, many times faster than he is (with the exception of one item in the new version). This is especially bad because previous game Sonic R had everyone else using karts while Sonic just plain ran, and that worked fairly well. So why the hell does he get forced to have a board now?
WRONG! The only characters who used vehicles in Sonic R were Amy (who had yet to receive her SA 2 speed boost) and Robotnik, and the whole game was oddly slow for a racing game. Meanwhile, in the first two Sonic racing games, Sonic Drift and Sonic Drift 2, Sonic did use a kart. It looked like his shoes. Even if those hadn't happened, though, I don't see what's wrong—Sonic's not a beam of light, things are allowed to be faster than him.
...Speed is his whole thing, he's the 'fastest thing alive', saying that some hoverboard is faster than someone that can move like he does is somewhat stupid
So hoverboards are alive now?
For what it's worth, in Sonic Battle Shadow was faster than Sonic. So "Fastest Thing Alive" is probably an outdated title.
It's been shown that Shadow's actual leg movements are slower than Sonic's. Shadow's rocket skates are responsible for his ability to keep pace with Sonic. And if '06 is to be believed, they're not doing as good a job of that as they used to.
plus he was just following the rules of the competition
This. Just because Sonic can run as fast as the competition without a board or kart doesn't mean he has to. This troper rationalizes that he would be happy to follow the rules of the race, as he still gets to go fast.
This is the explanation I give—that Sonic has to follow the rules, and being Lawful Good, if he enters a competition, he'll try to comply as best he can. You wouldn't run in a sack race. Sonic won't run in a car race. That being said, the whole thing about Sonic being "the fastest thing alive" was a product of the SatAM cartoon. This has never been canon in the games. Plenty of things have managed to outrun Sonic, alive or not.
I seem to recall that the above is actually the official explanation for why he doesn't automatically smoke all of the other racers in the Olympics games: he slows himself down in the interest of fairness. So this explanation is most likely canon.
A second note to go with above, if you read the bio for Sonic in Sonic & Sega All-Stars Racing. It states that he can run faster then everyone in the race but to be fair he rides in a car. Whos to say its not the same for the rest of the series.
I've heard that Sonic himself lampshaded the kart-racing deal in one Archie comic, where upon being asked why he drives a car, he demonstrates by finishing a race in just a few seconds on foot.
As for him boarding outside of a racing context in the series, whenever he does, he's typically training for the races ahead(Green Cave, Splash Canyon, Metal City if you want to be technical), traveling through places where using his gear would be beneficial(Babylon Garden, Gigan Rocks, Crimson Tower) or he just happened to have his gear on hand and figured it'd be better to use it than to just lug it around. (Megalo Station, Aquatic Capitol) Besides this, it's THE POINT OF THE GAME that he uses an airboard.