Worthless post is worthless by definition. "Gullible" is a much more subjective description as its meaning leaves greater room for ambiguity.
However, I'm sure we can all take comfort in the false security of consensus that Obama is qualified to be president.
Granted that a worthless post is worthless. However, "gullible" has a much more straightforward definition than "worthless". Something "being without worth" has far greater potential for explanation than merely someone who is naive.
And I was agreeing with you about Obama. If your method of trolling is merely to mirror a victim's post, I suggest finding a modus operandi that is easier to sustain.
I'd say he's more qualified than McCain, who spent years living in a Communist country.
His years in Vietnam are not what make him unqualified.