Socialism is intrinsically flawed. The more the government gives you, the more it needs to take. Limiting liberties due to the burden of heavy taxes. It wouldn't be so bad if the returns were 100% of what you put in. Therein lies the flaw. Hell, even 80% back wouldn't be bad. The problem is, we don't get that much in return. The bigger government gets, the more it costs. Yes, some socialist programs are good but we also have to think of the cost.
This is where I don't see Bernie as the big bad socialist candidate everyone is making him out to be. For the United States, we would need to completely gut and throw out the current governmental system and implement socialism from the ground up... that whole 100% in and 100% out. There is no way we could do that with our government the way it is now. So I am not worried about that.
Even without the freeloaders, those who can't put into the system and those who make poor life choices, the possibility of corruption and the enormous cost of socialism makes it flawed in my eyes. The idea that we can "save" everyone, though noble, is just impractical.
If you're the smartest person in the room, then you're in the wrong room.