You can certainly think that neither is fine, or that both are fine, but I'm not sure that there is any "surely" about the fact that if one is/isn't fine then the same must necessarily go for the other.

There are plenty of areas of regulation where professionals/people in position of trust are held to higher standards than individuals - for instance there are plenty of things you are allowed to do when you cook that a restaurant would not be allowed to do, health and safety regulations that apply to hotels whilst people are not subject to anything as stringent in their own homes and so on.

Conversely, in the context of B2B vs B2C, companies and providers are perfectly entitled to tolerate things from the C which they would not from the B. In the specific context of airlines, we already know that this is the case and that airlines sometimes "punish" TAs for things that they do not necessarily enforce with individual customers. For some airlines, that's notably been the case with some issues relating to hidden city ticketing (some airlines, notably in the US can go after individual customers too, but in Europe, that is certainly not common).

There are both "moral" and pragmatic reasons for this imbalance. The "moral" aspect (for lack of a better word) is that airlines entrust agents with a number of processes which they do not entrust individual customers with, so in a way, it is not illogical that they also consider that if a TA is not worthy of their trust it will have implications. The pragmatic reason simply has to do with volume. There might be little value in an airline trying to track mildly dodgy behaviour on the part of an individual - simply not worth the effort. By contrast, the same mildly dodgy behaviour on the part of a TA which sells thousands of tickets with the airline in a given year may be worth their while in debit memos/recovery.