If you have rules, you have to enforce them, especially when clear violations are brought to light. Otherwise, there's no point in having rules.
Allowing officials to selectively enforce rules means that, if something funny happens, they control the outcome with no accountability. The whole point of having written rules is to lessen the influence of officials over the results. You don't want the outcome to depend on how some official feels that day, or on who they personally like/dislike.
By the same token, do the rules in this case spell out what the penalty is for receiving inappropriate assistance? If not, then that's a problem, because it again leaves it up to an official's judgement.
I know I sound like a robotic "law-and-order" guy, but I'm really not. I've just seen the unfairness that can result when the rulebook gets set aside. In this case, I'd argue that enforcing the rules as written is the lesser of two evils.
If you think that a racer being handed some gels by a spectator/coach should be okay, then lobby for the rule to be changed.