Is the Muslim Brotherhood a terrorist organisation? The new United States administration was debating designating the group as such, but backed down at the last moment last month. That is a serious mistake, for the US and its Middle Eastern allies.

This region knows the Brotherhood well. We have a long history with its ideas, with its followers and with the consequences of its teachings. Too often, in the West, politicians and academics get seduced by its political face. But we understand its ideologies and the devastation that they cause only too well.

Brotherhood supporters argue the group is open to participating in democratic elections. But the evidence contradicts this. The Brotherhood’s participation in elections masks a record of consistent failure. Two weeks ago, the King of Morocco fired his new prime minister, Abdelilah Benkirane, of the Islamist PJD party, because after five months, the PJD could not form a majority – the longest period of in Morocco’s recent history without a government.

Or look more acutely at the example of Jordan, where Islamists won 16 seats in last year’s parliament election. The return to the Brotherhood to public life came at the same time as the rise of ISIL-related incidents in the usually peaceful kingdom.

This brings us to the most serious and damning aspect of the Brotherhood: the link between its ideas and violence. Brotherhood members rarely espouse violence in public these days. But the ideas of the Brotherhood swim in the same swamp as those of ISIL.

In both cases, they espouse contempt for national borders and the sovereignty of national governments. They believe that the norms and laws of countries can be overturned, simply because they stand in the way of the Brotherhood’s political project. And far from uploading the rights of individuals, they believe that citizens are expendable in the quest for a supra-national power.

Like previous US administrations, this one talks a great deal about fighting terrorism. But the only way to properly address the roots of terrorism is to deal with the ideas that succour it. The same beliefs that animate ISIL also animate the Muslim Brotherhood, and it is only by dealing with those ideas that we can destroy this scourge that has caused so much suffering in our region.

The Brotherhood’s ideas must be pulled out by the roots, and the only way to do that is to deny them space to operate. By failing to designate them for what they are, the US is taking a step back. Time to reconsider.