No, being on drugs doesn’t, in itself, justify being gunned down by a police officer. What it might do, however, is result in behavior that might be perceived as threatening (and, yes, that perception might be strengthened by racial prejudice) to the officer. This is especially likely in the case of PCP, a hallucinogen that can result in “agitation” and “combativeness or violence”, among other effects. Therefore, whether Terence Crutcher was on PCP is a matter of significance.
To be honest, I completely forgot about this case (naturally, I was distracted by what was perhaps the country’s most historical election). It slipped my radar that it was reported (with, evidently, little to no discussion...at least on my Facebook wall) over a month ago that Crutcher did, indeed, have PCP in his system, according to a toxicology report.
I don’t believe that this incident conforms perfectly to any popular left- or right-wing narrative. It is enough for me to recognize it as a tragedy.