Income Inequality is when the best worker gets paid more because that worker produces more.
Every time wage levels are forced above (higher than) the actual value of the work done by an entry-level worker it causes major changes, but the most daunting are that the entry-level worker is then required to do more and have higher qualification/skills which in turn limits job opportunities to lower level workers. The capacity to produce something of value for a free-market by each human-being around each of us is varied, and sometimes severely limited by an assortment of factors such as location, ritual, culture, society, gender, health, age, disabilities, etc.
Societies and cultures do not have aims to ensure equality, but they sometimes aspire to create fairness. There will always be the human condition of unequal circumstances.
Why would anyone believe it is a good thing to pay the same wage amount to an average employee and to a superior employee? It helps in that thinking to ignore incentives for rewarding the best workers that produce the best results.
Some people don't want a fair & free market regarding goods & services tied to skill & talent because of many issues. But the main thing is that the totality of the problem is more complicated than just wiping out the minimum wage laws.
I tend to agree that Milton Friedman the Economist is correct on this area. The deeper unresolved problems pertain to perceived inequalities.
I think that many people are having concerns about the inequalities caused when winners and losers are being chosen by authoritarian sources. They might think high minimum wages will equalize things, but they are wrong. The complication they ignore is that reality has unequal circumstances, unequal capacities, unequal skills, unequal silver-spoons, unequal thinking, etc.
One interesting fact is that the minimum wage laws usually have exceptions that only a few clever businesses are able to utilize. These waivers are mostly out of the view of many people.
I do think the minimum wage rule hurts more than it helps. As usual, the majority of employers can't get the exceptions. It hurts the smaller employers and start-ups. Wage laws and labor laws together have put the neighborhood lemonade stand out of business. The minimum wage laws have negative effects for businesses in general, large and small in my opinion.