Benedict de Spinoza writing a reply in December, 1675 to Albert Burgh, a young “champion” of Catholicism, makes this spontaneous, striking comparison to Islam:
The order of the Roman Catholic Church which you so greatly praise, I confess, is politic and lucrative to many. I should think that there was none more suited to deceive the people and to constrain the minds of men, were there not the order of the Mahomedan Church [Islam] which far surpasses it.
From: Correspondence of Spinoza. Benedict de Spinoza (Author), A. Wolf (Translator), Kessinger Publishing, LLC; First Edition edition 2003, p. 354