It is quite possible to understand the efficient market hypothesis and not believe it. In fact I think that everyone who invests in the market in forms other than tracker funds doesn't believe it holds.

The efficient market hypothesis is a useful thought experiment but the assumptions required for its proof are unrealistic and it doesn't explain real world volatility.

I do think the thought process of 'what do I know that the market hasn't taken into account yet' is a useful one and that if the answer is nothing buy a tracker. The knowledge could be proper research that disagrees with the media about a company.