From: "the fireside book of chess"

Lasker says; only one to two pawn moves in the opening

Tarrasch says; Nothing so easily ruins a position as pawn moves.

Steinitz says; the king and queen pawns are only to be moved early in the game.

But, genius has no restrictions. 

Here is Marshall vs Rogosin

 

Pawns are indead the soul of the game.

Making pawn moves is not always a bad thing. Extending your pawns allows one to gain space and can limit the mobility of the other player. One can also create a large control of the centre by using pawns. On the otherhand, pawns cannot move backwards so too many pawn moves can leave holes in your position and create outposts for enemy knights.

 

There are advantages and disadvantages so i wouldnt say that pawn moves in the opening are bad. You must judge by each position whether what you gain by extending your pawns is greater than what you dont gain by extending your or by making some other move.