There is no cogent reason not to allow them. We embraced secular humanism as our god. We are not a Christian nation. Deal with it.
The Islamists expected at the cathedral include representatives from the Islamic Society of North America (ISNA) and the Council on American-Islamic Relations (CAIR). In 2009, both groups were confirmed as co-conspirators in a conspiracy to deliver funds to the Gaza-based Hamas jihad group, which regularly launches attacks to kill Jews in Israel.
This year, Hamas launched more than 4,000 rockets at Jews in Israel, often from within civilian areas.
Hamas is an affiliate of the Egypt-based Islamist group the Muslim Brotherhood, which was ousted from power in Egypt by huge public protest in 2012. Both CAIR and ISNA have close ties to the brotherhood movement.
So, you tell me whether those are not good reasons enough...
Are you a Christian?