I don't have a problem with it, the comments in the mail are right about medico legal risk and how much more it would cost if solicitors were involved. I think as well people tend not to be aware of how junior doctors struggle the hourly rate is not that high because of the hours they work (despite recent changes still more than average) and they have lots of additional training costs during the first two years not all of which can be reclaimed.
I'd rather a doctor supplemented their income this way rather than being too tired to do their job properly due to working extra hours or moonlighting
I did a year in a role that included medical staffing and was inundated for requests for any available overtime.