on Writing Explained:
One of the most entertaining uses for language is to communicate to other people the exact degree of their intellectual failings. William Shakespeare set a high bar for creative insults in the 16th century, and, since then, English users have continued to find new and exciting ways to express disdain.
Still, the old standbys are perennially effective. Stupid and ignorant have stood the test of time, but do they mean exactly the same thing?