I don't disagree the poor would be targeted or coerced to participate. I do disagree people would be "forced," en masse, to donate organs. I also think removing it as an option misses a lot of opportunities.
If you can't get government assistance because you have an "extra" kidney, and you need to feed your family, I wouldn't call that decision anything other than forced.
Is a government somewhere witholding assistance from anyone because they're not donating blood or an organ? Or is this a "logical conclusion" you presume it would be taken to should monetary compensation be made available to donors?