I couldn't agree more with the band.
We already had that tribute as an album, Post Traumatic, and its subsequent tour. Yes, I know that it was a Mike solo thing, but the other members grieved their own way. Grieving gets tiresome, even though you miss that person, eventually it gets to a point where you just want to move ahead and live your life. A Chester tribute at the shows doesn't let you move forward, and it's depressing. If they had waited so long to come back, it's to heal their wounds properly. Look what happened to bands like Metallica and Slipknot, the sorrow deteriorated the relationship between members.
This tour is about celebrating life, a new beginning. They're happier than they've even been in a long time. Why ruin that, even if it's just for a moment, making your new singer remember that she's filling the shoes of a dead man?
"But the fans..." It's been 7 fucking years, move on. If the closest people to him have found peace with his absence, I think we could too. Don't feed the parasocial relationship anymore.