No way how is this possible 
Stockfish and ChessBase disagree on a Slav opening
Sort:
Most of those 4. Nc3 games probably were 1. d4 d5 2. c4 c6 3. Nc3 e5 4. e3.
First of all, the fact that you lost with this move is in itself meaningless. However, if you play through enough master tournament games and monitor them with a strong engine like Stockfish, you will find there are many times when the variation they choose is the weaker as shown by the engine. There are reasons the masters do this. To avoid drawing lines. To throw down the challenge of a complex line of play. Even though the position might be an advantage for one side or the other, the counter play might be sufficient. Maybe they felt their opponent wasn't strong with a particular line, or even in the mood for it. Sometimes the reasons they choose a line against an opponent it's purely psychological. Look at Carlsen crazy sacrifice against Topalov in game one at Sinqfield this week, obviously a dubious sacrifice. Analyze it with Stockfish and you will see. Why did Carlsen do it? But getting back to your original position, White is simply a pawn ahead immediately and if Black retakes, White exchanges Queens and Black can't castle. You should try playing that position several times against an evenly matched human or computer opponent, I'm sure you would get the hang of the position and win some games.
I've compared hundreds of opening positions with Stockfish 6 and the ChessBase database (available free online at ChessBase.com, by the way), and they tend to agree. That is, the moves chosen by top-rated players, and their results, are more or less in line with the best moves that Stockfish suggests.
But I just came across one case in which they differ:
1. d4 d5 2. c4 c6 3. e3 e5!?
Here's what Stockfish 6 (depth 35/51) and Chessbase show:
4. dxe5: 0.88 | 50% (draw) with one game
4. Nc3: 0.24 | 69% with 89 games
Do we chalk this up to engines being sometimes not so good in opening positions, or is dxe5 really the stronger move?
Incidentally, I played dxe5 and got killed, so I wanted to see what I should play in the future if it comes up again, and now I don't know. Logic suggests to go with the experience of real players in actual games, but still...