I don't see any power imbalance that exists within the relationship here. Compare this with the laws that prevent a therapist from dating a client, which are in place because one party can take advantage of the other or blackmail them or have them involuntarily committed. That's a power imbalance.
I also think this is a very orientalist view of the industry. How many founders actually raise institutional money off just a deck each year, who don't otherwise have the skills to earn a lot of money consulting or whatever?
I'm not trying to defend the behavior here in any way, I just think that the reason why it's wrong for a VC to aggressively proposition a founder or whatever is different than, for example, what makes it wrong for an employer to have a relationship with an employee.
The power imbalance is pretty obvious in that kind of scenario. It's less of an imbalance if the entrepreneur is also wealthy and just raising money to share risk or build alliances.
Point is, if you have multiple millions of dollars, "do nothing" is always on the table, which isn't so for many founders.