Expecting people to stick to well defined and commonly understood terminology is not an "argumentum ad populum", it's the prerequisite to rational discourse.I imagine a lot of Americans view Islam as a movement with a very specific meaning too; that doesn't make it less ignorant. This is totally an argumentum ad populum fallacy.
Intelligent Design as a movement has a very specific meaning (CE linked you to a comprehensive Wiki article on the topic).
Edit: accidentally a word
Edited by GeneralQuery, 20 December 2012 - 04:21 PM.