The fact is, the constitution is vague generally, and that has good and bad.
On the good side, it does allow for some useful flexibility. On the bad side, it allows for reducing the protections.
This is a time when governments stretch words for political reasons, whether 'imminent threat' for the Iraq war or, well, 'imminent threat' for drone use.
It's not new - John Adams and Woodrow Wilson both had and enforced their own ideas of what 'free speech' was protected, and it didn't include criticizing the president or saying you were against a war. People were imprisoned for exercising a right of free speech for both.
On the other hand, when birth control pills were invented, did the state governments have the right to say, 'you, citizens, can not use that product, because we think it will increase immoral sex not for procreation'? Some state governments did pass laws to do just that, and the Supreme Court found the constitution protected people's 'right to privacy' to make those decisions, by flexibly interpreting the document.
The founders clearly wanted the document to have that flexibility - when they said 'all powers not granted here are reserved to the states and the people', it meant for the courts to find those unnamed rights and protect them - that wasn't 'jusdicial activisim' that was violating the constitution, it was following it.
However, when the judges find corporations are 'people' because corporate lawyers made a major effort to get that perversion into the law, flexibility did violate it.
This happened especially when one strong corporatist with an agenda for an activist court to create these corporate rights got onto the Supreme Court, Lewis Powell.
He'd come to oppose the public's power to stand up to corporations - he was on the board of a major Tobacco company while the government fought them. As a time when the Tobacco companies were paying for large campaigns to claim there was no evidence smoking was dangerous, later exposed as intentional fraud.
Thing is, for better or worse, any vague constitution is going to be interpreted politically; by necessity judges have to make up an interpretation to apply it. That doesn't always mean violating it, that's a different issue. But everyone loves to claim that the way they decide to interpret it isn't political, it's the 'correct' method. And that's generally pretty baseless.
Scalia was pretty direct about this recently in his activist comments about the Voting Rights Act. He just decided it's up to him to say that the Senate didn't mean its votes when it renewed the act 98-0, and he said that the fix for the problem is that the Senate needed help to come to the right decision to reject the law by having a judge who will say it's unconstitutional.
This is the same guy who said that counting the votes in an election could cause irreparable harm to one of the candidates, the one he wanted to win.
But of course he's an 'original intent' guy who has the only correct interpretation.