This is the same problem that plagued abolitionists in the 19th century, women's suffrage at the turn of the last century, civil rights in the 60s, apartheid in the 80s, and gay rights and refugees today, some of which had to be solved by counter-propaganda by those in power, and some of which had to be solved the hard way by those with little power loudly promoting critical thinking.
I think this hits on what I disliked about the quoted Russell passage. He uses "intelligent" as if it is objective and obvious who is included, and that it is those who he broadly agrees with. You're doing something similar by dismissing from your definition of "smart" anyone who is prejudiced or religious. It is clear to me that there are extremely intelligent people who are one or the other or both. What do you achieve by excluding them from your definition of intelligence? It is better to attack prejudice as misguided on its own, rather than as the product of stupidity.
This applies to Russell as well; in thinking his opponents are just stupid, he deprives himself of the ability to understand their viewpoint well enough to debate it. The worst way to win an argument is to think the other side is just stupid and you're just smart, so there's nothing to talk about.
You can call it whatever you like, but the reasons for one group being so certain and the other group being subject to propaganda still remain. The goal for somebody in the latter group who can think critically is not to convince the former group (very difficult, whatever you may call that group) but to get other people in the latter group to think critically as well.