God is very serious how He views the poor - especially when people choose to oppress them and take advantage of them because of their poverty. The warning that we are given here is about oppressing the poor. The poor by their lack of money and influence are people who have a difficult time finding a way to deal with people who trample their rights. They have no money with which to address the legal system. They have no power among elected officials to influence them outside of their one vote. History has proven that there are a couple of groups who oppress the poor. These two groups are the rich and those who want to maintain political power. The rich do so most often by not offering the poor a living wage when it is within their power to do so. In an interest in getting richer, they take the wages that the poor should receive and keep them for themselves. God offers dire warnings to those who do this. The second group are those who use political power to oppress the poor. Even within our government it is advantageous to prevent the poor from bettering themselves by setting up a welfare state that encourages dependence. This is often not recognized as oppressing the poor because it maintains the illusion that the person in political power is helping them. But any system which traps people in poverty is oppressive, even if it oppresses by handing out what at first looks like free money.
Those who oppress the poor are taunting God. Taunting is such an ugly thing. When those who have an upper hand mock those less fortunate, it is disgusting. The Hebrew word indicates a mocking and open reproach of someone else. This is done in a way that deliberately desires to agitate or humiliate someone. The truly frightening thing about this kind of taunting is that the one doing it is infinitely less powerful than God. Usually the stronger one taunts the weaker. Here although the person is stronger in what is openly seen (i.e. the powerful oppressing the poor) they are probably unaware that their actions are taunting the living God. This is the most foolish thing anyone could possibly do. I get a picture of a bully taunting a small child, unaware that their incredibly strong and huge brother is standing behind them watching the whole thing. In that situation, as well as the one mentioned here in Proverbs 14, someone is about to get a serious beat-down.
The wise man has mercy on the poor. He uses his position of strength and wealth to help them. The word mercy has the idea of being treated in a way we do not deserve. Therefore the wise and godly man remembers how God has treated him - and uses that as a barometer of how he should treat the poor. Maybe someone has become poor due to their own sinfulness. Even in this case we should show mercy and seek to help. This honors God because it reflects His own character in our actions. Whereas the fool taunts God by oppressing and taking advantage of the poor - the wise man wants a reward larger than the riches or power he can get on the backs of the unfortunate. He knows that in the end it will go well with the one who honors God.