The central wrong idea underlying the economic policies of the mainstream American "left" seems to be this: everyone except me and the person I'm trying to help is a robot who has neither their own feelings and rights nor the possibility of reacting to anything to I do in any way other than what I intend. Let me explain this.
- Example #1: The minimum wage.
Equality is more important than fairness, so we should force employers (on the theory that they're wealthier than their employees which is isn't necessarily true itself especially when you count debt) to pay their employees more than the labor is worth to them.
Not only does this harm the employer, it probably won't result in the worker being paid more. If you're an employer and you want to hire someone for $6 an hour - and the potential employee thinks this is worth it for them - but the government won't let you employ them for less than $10 an hour, you're probably just going to not hire that person. So the result isn't low-skill workers being paid more but low-skill workers being unable to find jobs. And hence of course more justification for "the poor are downtrodden in this capitalist economy, we need the government to help them!"
I should also note that this concept seems inherently untenable because it can't be upheld consistently. What about a favor? Are you allowed to do someone a favor for $0 an hour? Or if there's some special case against 0, how about $3? What's the actual difference?
- Example #2: Anti-discrimination.
In a world with a completely free market economy, being prejudiced would be a horrible business strategy. It deprives you of potential employees and customers and also vastly harms your reputation. But liberals saw a problem where it never existed and passed The Equal Pay Act. (Note what that means. Paying women less than men for the same work has literally been illegal in the US for 50 years. When a liberal tells you women still face that systematically, point out to them that they're suggesting they can sue the employer for it and aren't.)
You can't stop people from being prejudiced; but you can force them to hide their prejudice so the market doesn't punish them as described above, to be prejudiced in more subtle ways and lie and try to make up other excuses for why they're being asymmetric, which, if anyone is convinced (which certainly people are according to the leftist narrative), will only improve the reputation of prejudiced people.
Additionally, discrimination being outright illegal actually discourages employers from hiring women because they know there's a risk of them being accused of this and sued, and claims about such discrimination are often widely open to interpretation - note that the law uses language like "under similar working conditions". Who do you think's going to define what's similar?
- Example #3: Gun control.
This one is pretty obvious. The only people who are using guns to commit crimes are the people who aren't going to follow your laws against gun ownership; most of them probably either already have guns or can obtain them illegally and will be pleased to know their law-abiding victims won't be armed as well.
I read a wise sentence once: If guns are outlawed, only outlaws will have guns.
Also, and perhaps even more importantly, it's not like you can't mug or murder someone if you don't have a gun. Something like pepper spray is no less useful as a means of violence for most crimes. Even knives are pretty effective at exerting power over other humans.
Actually, you could make the argument - it says something that I've never once heard this articulated - that other weapons such as tasers are a sufficient alternative for defense and if done properly banning guns while making other weapons easier to obtain could make it less likely that a criminal could quickly kill a large number of people while still allowing defensive weapon use. This argument isn't entirely unreasonable when you discount the fact that gun control inherently involves threatening to initiating violence against innocent people, but at best this could stop new criminals from acquiring guns (it's impossible to confiscate the guns already sold to future criminals), and we should still consider that there's a cultural element of conservatives to own guns for reasons such as symbolic support for the Constitution, which doesn't carry over to tasers, so even still this would probably vastly decrease the likelihood of armed victims in cases of gun violence. You'd have a burden to prove that the net result is beneficial.
It's also important, of course, in any discussion of gun control to keep in mind the very important arguments that civilian gun ownership is an absolute necessity for defense against tyranny and also an enormous help against foreign invasion.
- Example #4: Communism.
Everyone will be equal! It's great!
Until the rich stop working because they're not receiving the benefits anymore. You can increase equality, but besides being theft it's going to drastically reduce the total wealth available because you've removed the self-interested incentive to work - you can just play all day and buy yourself food out of the communal wealth. It's demonstrably false that this would work because if we had a sufficiently strong culture of altruism to make it work, it would already be happening - people would be generous enough to just support the poor without being forced. You also wouldn't be arguing for a statist model of law enforcement because it would be painfully obvious that the poor would get protection more than amply from the charity of the rich.