No, he is discouraging PLing, at least in the form of leveling by doing nothing. Statesman wants people to have fun, and he considers leveling by doing nothing NOT fun, so since that's not fun, that would not be somthing he wants people doing. But he can't stop you if you really want to. Though in the future with the increasing difficulty of the higher level game it should be less of a problem because people should run into trouble with an inadequate team per team size for missions anyway.
But yes, PLing is a form of cheating the game by getting levels you did not earn. Paying for a gaming service does not entitle you to get to level 50, be it in one month or ten. Cryptic will not say: "Oh, it looks like you haven't surpassed level 20 for over a year now since you've subscribed, we need to bump you 10 levels to get you up to speed." All the subscription does is allow you to play the game, you are not purchasing any leveling rights by paying for the service, nor by already having a higher level character. For example what you've earned as a lvl 50 blaster does not credit one towards a lvl 50 controller as you did not work for that controller and played for it to deserve it. This applies to all ATs and the variations of them. What makes anyone think that having a higher level character allows them to have another for less work or free is beyond me. That's like saying, "since i purchased this expensive car which i worked really hard to get the money for, i deserve another". Sorry, but the real world doesn't work that way, and gaming world social contracts are a microcosm of the reality that they are trying to create, and in this case, a world like ours but with superheroes and villains- NOT a world like ours but with superheroes, villains, and insta-high-level-hero-creation or cloning perks.
[EDIT: more stuff i wanted to add]
To the people that say what someone else does will not affect you. Stop deluding yourselves. Easy example: the U.S. presidential ballot. If it weren't for Florida... well i think you know where that's going. As a result of that, a monkey may have sent some of your friends and family to fight a war on foreign soil and lose their lives for it. Still not convinced? I doubt anyone of you know me but if you read what i post, i will affect you. Even if you disagree, or even forget, or anything short of a lobotomy, after all is said and done you will still have that lingering gut feeling that someone opposed your opinions, and that would be me and all the others who share an opposing view.
To the people who say that they can play the game THEIR way: We are playing the devs' game. We can only do what they have let us do. Hence when they find something wrong, they will fix it (or what some of you have lovingly dubbed "nerf"). You're not going to be able to play a lvl 99 hero, have every power on one hero, have infinite endurance, etc., just because you want to play that way. If there are ways to play that they do not intend, that is just a flaw that they haven't gotten around to fixing yet. Give it time. Just because something hasn't been dealt with doesn't mean it's "working as intended". The devs are people too and have other things to deal with than pamper us with extra code to keep people playing the way that's intended.