I guess we'll have to agree to disagree on the level of difference between giggling at Kirk or decorating his shirt with "Kirk is a Jerk"...
The thing is, though, that the computer in all Trek shows is in the habit of answering questions not asked by the heroes, thus displaying an advanced sense of plot. It's easier to think of it as Pakled type of cunning (language inhibitions hiding passable intellect) than as an utterly moronic automaton. TAS "The Practical Joker" could well represent the computer's day off, much like TNG "Emergence" does. Hell, both times the preferred means of AI self-expression is the holodeck!
Agreed, though, that pitting "Yesteryear" against some more closely matched opponent such as "Mudd's Passion" or "More Tribbles" (both delving deeper into an established beloved TOS character, although lamentably not past wading depth) would have been less unfair.