It's the dehumanisation which is wrong.
For me this is the crux of it, but I sometimes find it difficult to communicate what it is about with people.
As far as comparing it to other jobs, it may be that there are other people in the workforce we essentially treat as subhuman. Maybe not people around us so much, but what about the people working in places overseas producing for very low prices all the things we need or think we need?
But the point there isn't that sex work is better or justified by that, but rather that no work should be like that. We shouldn't accept that. If people think of burger flippers that way, and there are people trying in some countries to live on a burger flipper's wage, that is the wrong way to think of those people.
Where I find an impossible impasse is that there are a fair number of people who see a lot of non-commoditised sex from the same dehumanising perspective. Maybe it's freely chosen, but it's still fundamentally self-centered and using others as an object. If people think that is ok, even a good way for sex to be, they are unlikely to see sex work as a problem.
It can also be difficult to draw a line. Obviously prostitution is sex work. Nude modelling? Cam work? Getting naked on an HBO show? It's arguable that maybe we should only ban the ones that are more serious, but then when you have the young women on the HBO show, it's difficult to say that's fundamentally different than what some of the others are doing, and if people are taught to think it is ok they will tend to see those other things from the same perspective.