My values are the best that I know; I assume you feel the same.
Changing them is hard – it takes some combination of (delete as appropriate)…
experience / evidence / awareness / engagement with an argument / a strong feeling…
…of / with / about …
the flaws in our existing values / the way that something we think is “good” doesn’t map onto our values the way we thought it did / a better alternative
… for us to change our minds, with experience and story being far more effective than argument.