I was thinking, also, that “pleaded” is incorrect, but look at this:
http://www.abajournal.com/news/article/is_it_pleaded_or_pled/
This looks like another skirmish in the prescriptiveness versus descriptiveness wars. Prescriptive means using something as set down by the rules. Descriptive is simply noting what is out there and going with the majority.
Take your pick. I suspect conservatives tend to be more rule-following than liberals and that’s how it would break out in this matter. But that’s just a guess.