Now I don't hustle that hard really, I move on pretty fast, but even if I did I would not consider it the same at all. I do think the differences between the two behaviours highlight some of the problems you're having and therefore I will explain some of them.
1, In the case of hustling, hustling for dances is simply a part of the agreement. As soon as you enter the strip club it is agreed that money can be given in exchange for lap dances, private dances, good company etc. You, on the other hand, operate inside the club but outside of that agreement and that's where some of the issues you have come from. The dancers you pick are torn, partly because in the agreement they made at the door it did not say anything about fucking customers. Now as I write this I can imagine some blues might get their panties in a bunch and will try to argue that OTC is part of the "agreement" in strip clubs in general and let me just inform you now that you're plain wrong. Many strippers go through their whole career without any OTC action because they do fine without it and don't need it. Most strippers go into the club with the intention to strip, just as many customers go into the club with the intention to spend money on strippers who strip. That's the basic nature of the club, the agreement.
The problem you have OP is that you ask girls to do things that are out of their comfort zone. They were obviously not prepared and indeed one of the behaviours we're discussing here is not part of the basic strip club agreement and yes it is the one where you try to get unwilling dancers to have sex with you by "catching them at the right time".
2, Strippers usually have the goal to make it worth it, they pay attention to customers' pleasure and joy, that's how you make repeat customers and get a good reputation. You mention lonely and emotionally weak men and yes, lonely men sometimes want some sexy company too. If I am good company then why shouldn't the lonely man (considering that he is also a strip club customer in a strip club talking to a stripper) join me and have a great evening instead of being lonely and sad? A sincere question. What is predatory about offering a service that someone obviously needs and enjoys, even though they might not initially be completely convinced and in a happy party mood? When I hustle I do it knowing I have something worth paying for, I do my part knowing that if their expectations are in line with the rules of the club they will get their money's worth.
You on the other hand left these girls crying, it was not worth it for them. It was not a good experience. My goal is to make customers feel good and your goal is to make these dancers make you feel good. Again here is a big difference. The main goal for you is your own pleasure, not theirs, and it is also another possible part of the problem that you have; what you have to offer in this is money and while that can be important it doesn't take much effort which means that you can get away with treating these dancers in a way that I could probably not get away with as a stripper. As others have pointed out you could be unintentionally making the interaction more unpleasant than it has to be.
3, You ask how sexually predatory behaviour is any worse than "financial" predatory behaviour? I will use a metaphor here to describe my view on this and to put it short and sweet if someone put a gun to my head and demanded I steal someone's money or rape someone I would go for the robbery every day of the week. And please everyone don't make me hold your hands now and explain how I'm not accusing anyone of a crime or whatever, this is of course strictly a comparison of different predatory behaviours and the different natures that they do have. Sexual predatory behaviour will, to me, pretty much always be worse than a financial predatory behaviour and if you don't understand why - tough luck.