President Obama's reaction to the Egyptian military's killing of more than 500 pro-Morsi protesters in Cairo was about what we have come to expect from him in foreign policy, and that's not a compliment. Faced with a necessary, unpalatable decision on aid to Egypt in the wake of the 3 July coup, Obama continues to duck it.

Instead of addressing the issue of the coup and its implications for US aid to Egypt, he announced that the US would not hold joint military exercises with the Egyptians, which was just about the smallest punishment that he could have chosen, short of doing nothing. Had it not been for the extraordinary brutality of the crackdowns on encampments of Morsi supporters in Cairo, it is doubtful that the administration would have done even this much.

Beyond that announcement, Obama repeated what has become an increasingly stale slogan:

We don't take sides with any particular party or political figure.

This has been the standard administration line in response to several of the Arab uprisings since early 2011, including the original anti-Mubarak protests. But this has lost whatever appeal it may have once had when it serves as cover for supporting an authoritarian regime engaged in a bloody crackdown. Refusing to take sides in Egypt's internal politics would be the right position to take – if it were actually US policy in Egypt, but it isn't.

The US may not be endorsing specific parties or individuals, but it is tacitly endorsing the coup and the government that was created by it. Unfortunately, this manages to combine a bad policy of supporting the Egyptian military regime with the insulting pretense that the US is merely a passive observer, instead of a patron, of the offending government.

Much like Obama's Syria policy, his reaction to the violence in Egypt seems guaranteed to please no one in Egypt or the US. The US isn't in a position to improve conditions inside Egypt, but it does have control over how it reacts to events there. By law, the US is obliged to suspend military aid to Egypt because of the military's role in deposing the elected president. Following this week's brutality, Washington has the perfect excuse to do what it should have already done weeks ago.

There should be no illusion that suspending aid to Egypt's military will force the generals to change their behavior for the better, but similarly, no one should believe that the US retains any influence or "leverage" in Cairo by continuing to keep the aid flowing. All that continued aid shows is that the US is willing to tolerate virtually any wrongdoing by its client, no matter how blatant or destructive it is.

At best, Washington is enabling harmful behavior that it says it opposes. At worst, it is actively encouraging Egypt's military to follow its own worst instincts.

Many things around the world truly are beyond Washington's influence, and many recent American blunders have come from overestimating what the US can achieve overseas, but it is within America's power to have some minimal standards for what it expects from its clients. It is not news that the US has one standard for its allies and clients and another for other states, but ignoring US law in order to maintain that double standard on behalf of a brutal military regime takes this foolish practice to new extremes.

Unless the US takes much more significant steps to distance itself from what is happening in Egypt, it will keep taking the blame for the behavior of a client government over which it clearly has no meaningful influence.

• This is a longer version, written for the Guardian, of an article originally published by the American Conservative