The reason that conservatives and liberals disagree is because liberals judge their policies by their intentions while conservatives look at their outcomes.
To take minimum wage laws as an example, liberals think that the notion of a person working for $1 an hour is terrible, to which their remedy is outlawing any wage lower than, for example $8 an hour. Having accomplished this, they feel good about themselves because in their minds they've helped the poor.
Conservatives, however, look at the results of this policy and note that despite its best intentions, those who would have previously received, for example, $1 an hour, don't actually earn $8 an hour under the new law. In fact, they receive $0 an hour because the business simply can't afford to pay them that kind of rate. As a result, these employees will never accumulate the skills that at some point might have been able to earn them $20 an hour.
And while liberals protest that free market capitalism exploits workers because it allows employers to pay them as little as possible, conservatives point out that the term "possible" isn't absolute because it accounts for competition. In the same way that consumers can't simply hire a plumber at any low rate of their choosing, employers will not find it possible to hire willing workers at any low rate of their choosing.
Liberalism is an intoxicating ideology because its proponents can feel good about themselves without having to do much thinking or investigation. And because of this, it's almost always true that every liberal law results in the exact opposite of its intention.
Economist, investment advisor, author and commentator, Peter Schiff