It's worth reading the full post. It sounds like the Russian embassy has been shopping a lot of stories around, either directly or through proxies, and Pugliese has cited some of the evidence they purport.
One of the reasons the intelligence community was so dismissive of [KGB documents about recruiting Pugliese], I’m told, is because it is entirely in keeping with KGB tradecraft that they would try and recruit any and all left-leaning student-activist-cum-journalist in Ottawa. That absolutely does not mean they succeeded. Nor does it mean that Pugliese, had he been successfully recruited, kept up his cooperation into present day.
Beyond that, there are good indications that Pugliese may have been relying on the Russian embassy as an unnamed source, a decision I find ethically dubious, but far from traitorous.
As Ling mentions Pugliese has done some great reporting over his career. It sounds like DND has been trying to discredit him for a while.
I will take Chris Alexander's statements under advisement until we know more.