Scott Walker's attempt to de-unionize the public sector in Wisconsin was a nasty piece of business. Walker sprung a far-reaching bill he didn't campaign on that was designed in large part to hamper the opposition party from winning future elections.
It was not, however, a coup d'etat, as Robert Reich calls it. Walker duly passed a law through a duly-elected legislature. It's a highly unpopular law, but his opponents have democratic recourse: first a recall procedure, and then the next election. If Walker's law does not grow more popular, Democrats will overturn it when they next attain a majority, which will itself become easier due to the unpopularity of Walker's actions.
There's always a temptation to attack the procedural legitimacy of bills we don't substantively agree with. That's tendency was on wild display during the health care debate, when conservatives threw fits over President Obama passing a more moderate version of the health care reform he campaigned on. (Remember bouts of right-wing hysteria over routine legislative procedures like "demon pass" and budget reconciliation?) Conservatives are forgetting every single procedural complaint they made about rushed-through reforms that lack popular support -- has a single right-winger who made a fuss over health care carried his objection through to Wisconsin?
But that doesn't justify liberal mirror image behavior.