That is, if they are indeed true.
X killed thousands of babies without mercy
X killed thousands of pregnant women without mercy
X killed thousands of men, women, and children without mercy
X killed thousands of animals without mercy
X spared thousands of virgins for use by his minions
No matter what good things I now told about X, you would still have sufficient information to decide whether X is merciful or not if that was the question put to you. You would, as I would also.
Furthermore if we both know X very well, we now have the alternative to simply reject all of the above facts as false. We understand that this information all comes from dubious hearsay sources and is not valid. That makes for a completely different judgement to be rendered, IMO.