I don't think anyone is forcing anybody to invest in risky securities. The 1980s was worse with junk bonds and then no Fed QE. The FED is just doing its job to keep unemployment from rising. It's the mandate they are interested in and stock market rise is a secondary effect.
Who is morally responsible is irrelevant. Unless you're going to get a check from the Fed to cover your losses, you are the one who made the trade.
But people also spend more and feel good when their salaries go up. People tend to spend their income not their investments. Even if there was no stock market people still would be spending more if economy gets better.
I believe the FED is responsible for the money supply. A continually rising market in the context of an economic stagnation is a symptom of currency debasement. The purpose of the FED is to prevent the government from running out of money. They do this by debasing the currency.
At crisis times or times when the economy is about to see the recession, FED compels the citizens with their pressurizing economic policies, to indirectly buy the government bonds. May take up the revenue with this kind of policy but long run again the situation comes but with more difficult to handle as happened now for US like all the shut downs and inclined unemployment rates.