Vermont Sen. Bernie Sanders has been taking time away from preparing for the second Democratic debate, which will be held Saturday, to focus on supporting government workers who are demanding a $15 minimum wage. But that doesn't mean he wasn't also tuned into the fourth GOP debate Tuesday night. Sanders' responses to the debate showed just how much the corporations behind many of the Republican candidates' campaigns really peeve him.

Sanders tweeted that the minimum wage has got to come up at the beginning of the debate — all of the Republicans said it should stay at $7.25. And his responses in general made it clear just why Republican plans for the economy wouldn't do anything to address income inequality in the United States — a key focus of Sanders' campaign. In to a tweet sent just as the debate was ending, Sanders wrote:

Republicans should worry more about their kids and grandchildren and the future of this planet than their campaign contributors.

It was right on topic, given that the focus of the debate was the economy. Many of the GOP candidates said that they wouldn't cut taxes for corporations, but would instead institute a flat "fair" tax. But it seems like they would have some kind of conflict of interest in this, if they're taking money from the same corporations whose tax code they would later help craft.

And this wasn't the only issue that Sanders called Republicans out on during the debate. The event was held in the Milwaukee Theatre, where Theodore Roosevelt once gave a 90-minute speech after being shot in the chest. Sanders clarified just what Roosevelt would want as far as economics policies go, and also called out Trump for the amount of tax breaks he receives:

A few hours before the GOP debates began, Sanders tweeted, "American immigration policies should be about uniting families, not separating families," and "We cannot and should not sweep up millions of people — many of whom have been in the US for years — and throw them out of the country," obviously in a direct nod to Donald Trump's plan to deport all undocumented immigrants from the country if he is elected president. On ABC News' This Week Sunday, Sanders delivered his most direct and scathing critique of the Republican presidential candidates, saying, "On her worst day, Hillary Clinton will be an infinitely better candidate and president than the Republican candidate on his best day."

Sanders, who refuses to take campaign donations from big companies, was right to call out the candidates for taking money from the same corporations who would be regulated by their policies, should they be elected. And his critique of Trump showed just why cutting taxes for the rich — or having the rich pay the same proportional tax — is anything but "fair."