Stupid question....did you have a quest when you went there, or did you just go there on your own.
Got a quest from a sinper in Novac (NOT Boone) to chase ghouls out of REPCONN by whatever means necessary.
If you were in the top floor (the dark room with the dead cows & metal looking platforms in it has the stairs up to it) and killed all the ghouls up there, including a special glowy-green looking one, yes, he was important to a side quest. But....I'm not entirely sure you have to do his stuff to actually complete the main objective (get rid of the ghoul problem for Novac), no matter how you acquired the objective. It's possible if you just kill them all & the nightkin, that would work too. I've never tried it that way.
I (or rather, first Ed-E-ot and then myself) shot at anything that showed up as red on my compass. Didn't notice any green glowy ones among the ghouls, but if there was one, he must have been hostile by default.