Much as I dislike unions, I'm afraid that they are the ONLY way that you'll get industry-wide minimum pay and conditions.
As a profession, Acting is a classic area where there are a near infinite number of people willing to work for free: to "get their foot in the door", to "get known", to "build the CV", etc. Similarly, musicians. How did they sort themselves out ? Equity and the Musicians Union. Anyone hires a non-union actor or musician, or tries to pay them less than the industry minimum, everyone walks. Result ? Anyone who wants to tread the boards for a living gets paid. Not a lot, but they get paid.
Unless and until something like that happens in the helicopter industry there is no way whatsoever that you will stop people flying for free - they need the hours, the operator wants to make a profit, everyone's happy. Fulminating about it bringing down standards or reducing the going rate for everyone else won't help.
As I say, I'm not advocating "Rotary" the helicopter pilot's closed-shop, but there is no other way.
Another thing. What constitutes "flying for free" ? I've ferried a number of aircraft between School and Maintenance organisation in the past, for nowt. Does that make me scum stealing the bread from the mouths of starving CPLs, or a nice chap helping a CFI slope off home early ? And to be honest, if I could pick up some ferry flights now, I'd take them, to get my feet off the ground and to reduce the cost of the mountain of hours I need before an insurance company will allow me to earn some money.