It is illegal to "take" a pickerel under 15 inches:
http://www.mass.gov/eea/agencies/dfg/dfw/laws-regulations/plain-lang-sum/taking-of-certain-fish.html
...and I would tend to think that "killing" counts as "taking." (I mean, is it really "catch and release" if you release them dead?)
If pickerel outcompeted bass then I would expect to see "pickerel ponds" and "bass ponds" -- pickerel ponds where the pickerel outcompete the bass, and bass ponds where there are no pickerel to outcompete the bass), but I only really see mixed ponds. If there is one, then there is the other. So I don't think either outcompetes the other. They cohabitate the top of the food chain.
I don't mind pickerel when using a mat punch rig -- they're not gonna cut 50+ pound fluoro braid, and some of them put up a terrific fight.
Don't kill the pickerel... if you're catching pickerel then you know you can probably catch bass in that spot too, they don't really outcompete the bass, they are just more aggressive, it is illegal to kill the small ones and the big ones are more fun to catch than to kill anyway.