I was going to jump on you to disagree, but I think you're partly right in that some people do understand something different from the word.

Still, it's important to understand that there are people who disagree with you, and who do things that you view as objectively wrong, that are driven by idealistic impulses.

Do you conflate "idealistic" with "good"? Similar to the sibling comment, I do understand people have different mental definitions, but idealism [esp + vast power] can and often does lead to fairly awful outcomes, this is afaik well understood. It just seems that you're misunderstanding what idealistic means