Pretty much every movement does this sort of thing.
Religions: "Catholic" actually means "universal" (implication: all the real Christians are among our number). "Orthodox" means "teaching the right things" (implication: anyone who isn't one of us is wrong). "Sunni" means "following the correct tradition" (implication: anyone who isn't one of us is wrong").
Political parties: "Democratic Party" (anyone who doesn't belong doesn't like democracy). "Republican Party" (anyone who doesn't belong wants kings back). "Liberal Party" (anyone else is against freedom).
In the world of software, there's "Agile" (everyone else is sluggish and clumsy). "Free software" (as with the liberals: everything else is opposed to freedom). People who like static typing systems tend to call them "strong" (everyone else is weak). People who like the other sort tend to call them "dynamic" (everyone else is rigid and inflexible).
I hate it too, but it's so very very common that I really hope it isn't right to say that everyone who does it is empty-headed or empty-hearted.
The charitable way to look at it: often these movements-and-names come about when some group of people picks a thing they particularly care about, tries extra-hard to do that thing, and uses the thing's name as a label. The "Rationalists" are called that because the particular thing they chose to focus on was rationality; maybe they do it well, maybe not, but it's not so much "no one else is rational" as "we are trying really hard to be as rational as we can".
(Not always. The term "Catholic" really was a power-grab: "we are the universal church, those other guys are schismatic heretics". In a different direction: the other philosophical group called "Rationalists" weren't saying "we think rationality is really important", they were saying "knowledge comes from first-principles reasoning" as opposed to the "Empiricists" who said "knowledge comes from sense experience". Today's "Rationalists" are actually more Empiricist than Rationalist in that sense, as it happens.)