Not really. Did democratic nations violate their ideals when they fought Nazi Germany in WWII?
After all, Hitler did come to power democratically. He made it very clear what he wanted to do, and the Weimar government didn't stop him, thinking that they could just have voters see through his act. How'd that turn out?
An empty rebuttal. If the US democratically - by popular vote - decided to annex Canada would that mean Canadians waging war against the US or allies that stepped in to help them were going against the ideals of liberalism? There's no paradox to be had there. It is entirely possible for multiple liberal parties to disagree and end up at war.
Where people like to apply that phrase is when handling domestic affairs in a blatantly hypocritical manner. Such as banning certain speech, publications, or political activities while still claiming to honor the tenants of liberalism. In that context it's nothing more than a fig leaf to cover for one's own lack of integrity.
After all, Hitler did come to power democratically. He made it very clear what he wanted to do, and the Weimar government didn't stop him, thinking that they could just have voters see through his act. How'd that turn out?