To be fair, he did mention seeing blood. I think it's pretty clear that you should've hit if you see blood. I can see where he's coming from. It's not "oh, I missed, must be hitreg," it's "oh, there's blood but no death, god damn hitreg."
Ping only starts to matter after a certain point (granted, it's a relatively low threshold). When things are or aren't happening and ping is low, what else do you call it?
seeing blood means jack squat.
Source/hl2 (and other modern FPS games) uses networking systems that employ PREDICTION and LAG COMPENSATION to smooth gameplay and make the game look correct to the players.
but with lag compensation and prediction what you see and what really happen can be quite different at times, such as the blood sprites showing hits.
what you see is what your computer thinks will happen when you fire at that moment, so you may see a blood splat and impact but on the server end you may not have actually hit so then you yell at your monitor pointlessly "OMG F"ING HITREG"
with a 250ping it takes 1/4th a second for your fired shot to be sent to a server then another 1/4th a second for the result of that shot fired to be sent to you.
so without prediction you would have to wait a full half second to actually see your shot fired.
be aware also that the faster and more frantic a game is the worse the registration and prediction will get.
Prediction is just that prediction and a computer is not any better at telling the future then you or i can.
those who don't have A.D.D or A.D.H.D can read into how it all actually works:
http://developer.valvesoftware.com/wiki/Source_Multiplayer_Networking