If someone signed a contract to a Mcdojo...?

Tearing up the contract does not void it. That is against the law, unless both parties agree to it. Otherwise it is considered breaking the contract and that person will be held liable for whatever terms are listed in the contract for the breach. Usually though, there are ways out of contracts, but they are not often without early termination fees. Depending on the reason given, most can be talked out. Even if not, it's still better to pay $100 termination fee then continue with the payments and not enjoy or attend the cles until the contract runs out.