There are many ways to categorize and define argumentational fallacies, and so it is often difficult and disingenuous to argue over exactly which fallacy is violated by a particular utterance.
But since this is blown up since I last looked at it, why not take a moment to try to diagnose this.
It is not in fact an 'ad hominem', as you said, since an ad hominem attacks an argument by attacking a person (or group). Though it is, to me, perfectly fine to call it that, since that is the result, the second quote does not in fact attack any argument directly.
It is a response to the act of quoting Rand, rather than to anything specific that Rand was quoted as saying.
Secondly it is also not an 'appeal to emotion', since an appeal to emotion is again directed at making a particular argument, in this case by making people feel instead of think. This again does not fit the second quote, because it does not make any specific argument at all.
From what I can tell, the most descriptive term we can find for what makes this quote by 'John Rogers' so upsetting, as evidenced by the amount of discussion below and above, is that it is a 'smear'.
Its nature is that it does not attack the argument made by the quote it is posted in reply to, but instead attacks anyone who might believe, and quote, anything from that book, presumably including the OP.
To quote Wikipedia [1]:
> A [smear] is an intentional, premeditated effort to undermine an individual's or group's reputation, credibility, and character.
...
> Smear tactics differ from normal discourse or debate in that they do not bear upon the issues or arguments in question. A smear is a simple attempt to malign a group or an individual with the aim of undermining their credibility.
> Smears often consist of ad hominem attacks in the form of unverifiable rumors and distortions, half-truths, or even outright lies; smear campaigns are often propagated by gossip magazines. Even when the facts behind a smear campaign are demonstrated to lack proper foundation, the tactic is often effective because the target's reputation is tarnished before the truth is known.
> Smears are also effective in diverting attention away from the matter in question and onto the a specific individual or group. The target of the smear typically must focus on correcting the false information rather than on the original issue.
> Smear tactics are considered by many to be a low, disingenuous form of discourse; they are nevertheless very common.
So, while this is not strictly one of the traditional logical fallacies, I think it is nevertheless clearly a bad form of discourse, and frankly inappropriate.
[1]: https://en.wikipedia.org/wiki/Smear_campaign