We can’t stop them from running a full node (or a million full nodes), nor can they stop us. If a hard fork happens, it will result in two competing tokens, and then the market will decide. If their token loses value, they will rig the rules, and if they rig the rules, their token will lose value. In end the original token will prevail, as long as there is one person running a node to support it. If you believe in Bitcoin, run a full node and become unruggable.