On the face of it, what students of classical languages call the rule of sequence of tenses has been broken. If the situation is, as it appears to be, that the person speaking is is referring to some action that is in the past, presumably either disapproving morally of it, or responding unsympathetically to an unfortunate result of the action or considering the the action unwise and likely to lead in the future to unfortunate consequences.
There is one circumstance in which you might be able to defend the use of this modal present. If, the remark follows an exchange where the speaker had said something like "What a rotten/stupid thing to do!", to which the aggrieved party complained "Well, it's easy for you to criticise me: you aren't in my shoes." Then the speaker might have retorted: "Even if I were in your shoes, I wouldn't have done that." Then s/he would be saying the equivalent of "Even if I were in your shoes, I would not have done what you did (i.e. I would not now be in the position you are in of having done it and facing the consequences).".
But I am stretching credulity. On any reasonable construction of the sentence and its probable context you are quite right, and your suggested version of the sentence is correct.