Quoting wikipedia

Several reports have denounced the use of wikipedia in university assignments. This is rightly so. To conclude that wikipedia is therefore unreliable may be somewhat excessive. So is wikipedia generally correct or not? Is it free of bias or not?

I use wikipedia at least weekly. I think it is a useful source. As with all material, an appreciation for presuppositions helps one decide what he can and cannot use.

It is therefore appropriate to use or point someone to wikipedia for general information. But it is not helpful in argument to refer to wikipedia as an authority. I may have material on a subject; that some random editor has judged my material and found it wanting, or is unaware of its existence, or claims that it is an inadequate/ inappropriate source for use in an encyclopaedia (even if my material is true!)—none of that invalidates my material or argument. An appeal to wikipedia is merely an appeal to an authority with which I disagree; rather my material needs to be refuted on its own grounds.

So someone's reference to wikipedia at one time does not justify your appeal to wikipedia on the basis that he has done the same prior; he hasn't.

Encyclopaedias are more useful for breadth of knowledge, less so for depth, and they are inappropriate to refute those who knowledge of the subject is similar to the author's.