It's more actionable than you might think. Attitudes can be changed - by social pressure, through the media, and through education. And while legislation may not directly change attitudes, it can also help create pressures that reshape them indirectly.

I think the parent's point is "sexism" (and most "isms") themselves aren't specific enough to be actionable. There are many beliefs and actions that can be classified as "sexist". These specific ideas may be corrected. But "sexism" is too vague to be addressed itself.

The first step is to understand that the problem does exist, even if it may not be apparent, or even if we can find other, simpler or more comfortable explanations. That's all my reply could hope for at best. There are many smarter and better people than me offering plenty of detailed analysis and paths to action.