You can get carried on a stretcher after a year on ISS. You're on your own when you get to Mars. The trip back won't be easier. It might be survivable. But is it ethical?
If people are willing to risk their lives in the name of human progress, why wouldn't it be ethical?
The trip to Mars doesn't take a year, even unmanned probes that take low energy trajectories make it in around 200 days. And Mars has less than half the gravity of Earth, so you wouldn't be as crippled as here.