If someone is eminent danger to others and there is no other option, it's ok to kill them to in my book. But no it's not ok to torture people at al. But I make a difference between torture and imprisonment: since I think prisoners deserve humane conditions and rehabilitation should be the goal, prison should not be like torture. If your prison is torture you doing it wrong.
They wont, we have pretty good data that rehabilitation is a rather good way to prevent recidivism. It helps if the society is in general build in a more social way. But sure there are some people who can't be reintegrated into society and have to be kept in hopefully humane way separated from society, we do the same with extrem forms of mental illness.
It isn't an opinion, though, you are simply failing to follow the conversation. I said "the method itself", which implies that I am comparing this method to other methods and NOT discussing whether or not capital punishment is ok.
And you are not getting the point. Every method of killing people is terrible and inhumane. There is no humane way of killing people, because the very act of killing people is inhumane.
The only humane method is one that doesn't kill or harm people.
How is it ridiculous? If someone wants to end their own life, oxygen deprivation is possibly the most peaceful way to do so. In fact, many folks choose to end their lives with dignity by closing themselves in small "gas chambers" specifically designed for this purpose.