It is the restaurant owner's choice to "under-pay" their back of house staff in the first place.

Now, they're claiming equity by by taking the servers tips and giving it to back of house. Now that I think about it, that's what equity generally means around here: the picking of winners and losers.

Have a no-tipping restaurant. Pay your workers what you want. Do not, however imply that your under-payment of staff was the fault of the servers or customers.