A common feature of appeals to motive is that only the possibility of a motive (however small) is shown, without showing the motive actually existed or, if the motive did exist, that the motive played a role in forming the argument and its conclusion. Indeed, it is often assumed that the mere possibility of motive is evidence enough - this is not the case here. The "ad hominem" in question is a conclusion of a formed thesis found within the text of the meme. All points of which, are factual statements. Not so much as personally factual, but so far that yes, this speculation is a plausible theory to the politics behind the pro-life crowd. Thus, invalidating the accusation of ad hominem by appeal to motive.