Then I'd say 3 moron obvious hackers. I run across them once or twice a day, and since many of them really suck at the game we still win.
Well that's quite unlucky for you, assuming that these 'hackers' you speak of actually hack.
The players that are otherwise terrible at the game but hack are an annoyance. Most 'good' and high KDR players simply don't just 'derp' around and pick you off the second you come around a corner halfway across the map time and time again. Listen I have 2K hours in this game, I 'get' a VSAT, UAV, Team Call-outs, or you name it ... the morons I'm speaking of in theater are found scanning and looking for little red boxes. A 'good' player is constantly using duck/cover/drops/dolphins/etc.
We play in a team and it's not just 'my' opinion and many of us have 2-3-4+ KDR's.
To date and according to Activision there have been "...banned hundreds of thousands of players from Black Ops 2 alone..." ; see -> http://community.callofduty.com/thread/200752092 frankly I was surprised the number was so damn high, and I assume across all platforms as a TAC ban.
The '70%' is the over the top exaggeration.
Yeah I would have to agree that 70% is way too high, 7 out of 10 players using hacks? Honestly doubt it. Although I have to admit it that is hard to define as linear, I would gather that the statistics would be exponential seeing as Black Ops 2 is coming to the end of its life cycle. I guess I've just really been lucky to have only met 3 blatantly overpowered hackers. The subtle ones I can deal with.
Would like to say that the AC in BO2 is probably the best around. And they do a great job, however a 'certain' cheat that has been out since day one has over 112k downloads (so they say). That is definitely less than 70%, but that is just one company... so who knows.
IMO anything over one cheater per week is too much to bother with, and it's worse than that on PC.
I would tend to agree with @PaperTank that the number of over-the-top (blatant) hackers is very low. I've seen Glitching and moronic stuff like Death Machine secondary hacks. Most hacks (cheats) are subtle e.g. AimAssist AimBots and HUD hacks (ESP) and the idiots that make an ass out themselves will and do eventually get a TAC ban and thankfully recently the move towards VAC Bans.
However, to answer the deeper question ... yeah sure some folks have hacked for a long time and haven't been banned trying to pass themselves off as Pro level players. My best guess is 10%~15% hack and I have no idea the percentage that eventually get caught and banned. Many I KNOW are hacking have been doing so for far too long. Rentable servers is the best was to kick players off. Even if someone isn't cheating, most folks do not like high KDR players on their servers and those guys can rent their own servers and wait for people to show-up (que-in cricket's sound now).