Yes it is immoral and absolutely wrong. History is just that it is the record of what happened and should be kept for all time.
There is room to fill in history that is wrong if it can be proven through unbiased research. But it should never be bent to the whimsy of revisionists to suit their agenda.
Consider what we would know about ancient times if religious zealots hadn't destroyed all of the writings they could find. Should apologists be allowed to erase the Holocaust? No. But that doesn't mean that facts shouldn't be challenged and reconciled just because it might anger those who have stated them incorrectly.