I'll now explain what I mean by taking both your quote and your reply and dissecting how I interpret them:
> "childish fantasy" "lifelong obsession" "unbelievable heroes" "emotionally stunted, socially crippled adulthood" "unable to deal with the real world"
The argument here goes: people who like Ayn Rand are immature and live in a dream world, which means you should not listen to what they have to say because it bears little relation with the real world. It's pretty obvious what the ad hominem is if you use this quote straight after someone quotes Ayn Rand: it is targeted at the poster and implies he is, himself, immature, living in a dream world, meaning one should dismiss his arguments without consideration.
> I was tempted to reply with a "found the objectivist"
This one is on par with telling a new black acquaintance about your black friends, or sending them news about black people doing great things. I should not need to explain it, but I will.
First, your original comment, as explained above, painted all "Objectivists" (Ayn Rand "fans", for those unaware of her writings; she groups her ideas under the term Objectivism) as immature dreamers whose arguments should be dismissed.
Then, you hint at what is on your mind, much as the man sending "black news" to his black acquaintance is hinting pretty strongly at the only thing he can think about looking at him. "I was tempted" might work in a bar discussion as a sufficient disclaimer, but HN is sophisticated and sensitive to such "fake disclaimers" (although those who point them out can be tarred with the "SJW" brush).
Your line of argument here is "I am stating that you are an Objectivist, therefore your arguments are not worth listening to because Objectivists are immature/unable to deal with the real world/see above". This is the literal definition of ad hominem, even if you hinted instead of outright stating. The context - HN, and its sophisticated audience and level of discussion - make it intentional and the equivalent of stating it outright.
You reinforce this line with the end of the sentence:
> but I'm waiting for a build, so I have time to kill
This really means "you are not ordinarily worth engaging with, because [see above], but since I have nothing to do, I will". This is reinforcing the ad hominem by introducing superiority and dismissiveness. "Here, child, let me explain."
> The quote I used doesn't attack the author, it attacks the work
It is extremely rare to attack a work using appeal to emotion without attacking the author. Usually, the best way to clear the doubt is to spell it out. You didn't. In fact, the brevity and context of the use of the quote, coupled with the fact it explicitly attacks Ayn Rand, imply the opposite.
> If you want to criticize it, you would do better to point out that the quote I used is not constructive criticism.
I did criticise it. Pointing out that appeal to emotion is not a valid line of argument is a constructive criticism. I have expanded on the idea earlier in this reply, but the core of it is that appeal to emotion attempts to use emotion to make you skip logical steps and accept a conclusion you might not have ordinarily.
> humorous quips rarely are
Ridicule is one of the most effective appeals to emotion. I could probably point 10 examples from the first 15 minutes of the Presidential debate last week. Even the words used by both candidates are carefully chosen (see [1]). Your particular quip is only humorous if you belong to the tribe that likes to auto-ridicule Ayn Rand readers (without having ever read the books or even the arguments), and otherwise serves to silence those unwilling to take the social penalty of speaking out against it.
Lest you think it is personal, it is not. Hell, I know where you're coming from - in a previous era, I was banned for several weeks from an internet forum for calling someone an "internet redneck" for presenting Republican-favouring arguments.
I am simply fed up with the rising market share of appeal to emotion in all kinds of domains from advertising (thank you uBlock, Privacy Badger etc. for making the internet useable for me again) all the way up to politics and the legislative process. This is my little contribution to fighting against this trend. And yes, the use of the word "fighting" is itself an appeal to emotion.
[1] http://blog.dilbert.com/post/147998060931/the-dark-and-rotte... - "The Dark and Rotten Election" - Scott Adams
