I've been on a CS:S server once. my ping was 120... It was a zombie server, you know a few CTs vs 16+ Zombie bots that took forever to kill, anyway one of the CTs was telling me to leave my ping is too high, it causes lag... I said no, it doesn't, 120 isn't a high ping anyway, of course he said that wasn't up to me and then banned me... Back with games like MoH Allied Assault, yes a couple high pings might affect everyone's game...
Half-life (and all associated engines: q2, q3a, hl2, hl, etc) do something entirely different: the server and clients agree on a shared, latency-adjusted idea of time. Each client timestamps their commands ('i shot over there at 1:31pm and 23.2 seconds') and the server then rolls back its view of the world to that time and sees if it the shots hit. In this way, people with high latency get a better game experience at the expense of those with lower latency. Those low pingers can now be well away from a confrontation when the server decides that the high pinger did, actually, kill you. Then you drop dead, seemingly at random. (You know, when you duck back behind a corner, Then get shot from when you rounded it)
In short, High Ping players do not cause lag to low ping players, but something that does: That ammo pile that often stacks up at Donner, when there are 50 or so boxes in there, and someone tosses theirs in, they all Nudge a bit (Physics!) and when they all shift for a second, it causes lag (I've seen this a million times in Garry's Mod) I brought the idea up that the lag might be caused by that yesterday, and when we stopped tossing them in and picked them up, the lag never reappeared, Just something to look into