That looks equally applicable to everything that is sold on the market, not only to crowdsales. Everyone should be free to invest in whatever they want, however, that comes with responsibility as well, everyone should do his own due diligence and no one is forcing them to participate. It's just like everything in life. Being able to participate in everything isn't an excuse not to take responsibility for your actions.
Following that same line of thought, gambling should be illegal. That argument doesn't make sense to me.