Whether you approve or disapprove of the actions of the men who allegedly carried out the attacks in Paris, their personal histories are irrelevant.
It is being said that they were sinful, used hashish, frequented night clubs, and so on. This information is supposed to discredit them as mujahideen.
I am not interested in defending their action or validating it as being correct in the Shari’ah; however, it should be said that even a lifetime of sin and disobedience does not disqualify someone from being a Mujahid. Indeed, jihad, and seeking martyrdom may often be motivated by a sincere desire to atone for past sins.
It is a strange logic which says that a person guilty of committing sins becomes a hypocrite by trying to perform what they regard as righteous actions to potentially absolve them of their many wrongs.
I do not know how Allah will Judge those brothers for what they did in Paris, but I am sure that they hoped it would please Him, and that He would Forgive them for whatever sins they committed in the past.
We can argue about the legitimacy or otherwise of their attacks, but their personal histories of transgression are not evidence against their sincerity in any way.