I believe in preaching an impossible ideal for which we should strive, as long as it is coupled with an understanding that it’s okay to not be able to reach it. The ideal itself often is what inspires us to do and become what we wouldn’t do and become otherwise. (One of my favorite songs is “The Impossible Dream”, and one of my favorite books is Don Quixote.)
Having said that, preaching an impossible ideal without understanding it is only an ideal is destructive. Preaching a physical ideal based almost solely on a subjective and cultural standard of beauty - nope, I don’t like that. I have four daughters, and I hope they NEVER want to enter a beauty pageant.
The Gospel is not a beauty pageant, and too often we forget that.