There's a lot of misconceptions every time I see these threads. No-life wall of text incoming.
#1 Releasing evidence
No reputable league or game company would ever release evidence on a players ban. It just isn't done. Ever. Is the average player competent or unbiased enough to be able to review such evidence accurately? The material is always extremely technical, we're not talking Youtube videos with bad editing and effects here, or ignorant comments like "that shot was bs". More importantly, cheats and anti-cheats is a constant cat and mouse game. Cheats improve, AC adapts. If cheaters are aware of the methods used for catching them, they will adapt. I've always referred to this as a double edged sword, because a player has no way whatsoever to defend himself after a ban. Nonetheless this is entirely necessary for the overall good of the league. The majority of people asking to see evidence do so to satisfy their curiosity, which is not the best of reasons.
#2 "But he's bad" "but he was on lan"
Some people assume cheaters are bad at the game, which can be incorrect. When common players think of cheaters they might imagine a very young person that do it blatantly in pubs with ragehacks, not developing their game sense and positioning/aim because of the extra help they get, but could you imagine a competent competitive player with just a simple % increase in his accuracy? Players skill is entirely irrelevant for an AC admin because it's actual technical evidence that is used. It can be done on any class (medic with esp for example) and it shouldn't matter if the player is high profile or, excuse the term, a nobody. Public backlash should never be a factor, and every case should be treated equally. A cheater doesn't necessarily cheat 24/7. It can be utilized on a random pub or on a crucial moment in an official where you need a medic pick, just to give an example. A person can go 0-20 while cheating and stats and logs are entirely irrelevant.
#3 "but he/she isn't Vacced?"
briefly looking at most of the the cheat forums in my bookmarks while writing this, i'm seeing 20+ public cheats that remain undetected, one famously being undetected and used since 2011. Keep in mind that these are public forum (ie script kiddie sites), and this doesn't account for private ones. Valve is really pushing AC into cs:go due to the dev support and how prevalent it is in destroying players experience in matchmaking. Only relying on VAC for a game like tf2 is just not realistic for a competitive league. Heck, even the donator version of LMAOBOX (biggest commercial cheat in tf2) remained undetected for a long long time through regular patches, although the creator now forces you to utilize a burner steam account to avoid his customers complaining about getting a VAC ban.
#4 "Vac is game specific"
Yes. Sort of. Doesn't hurt anyone if I talk about this because a banned cheater can do nothing to prevent it. A ban in cs:source for example carries into tf2 because of utilizing the same game engine and some cheats are usable for both games, so Valve simply included most Source games together, exception being cs:go and Goldsrc games. You can't directly tell on a users profile what game a VAC applies to, but every items that's not bought in the store is queued to be removed from their inventory, usually within 24 hours. Sidenote: I really think Valve should consider showing what game a VAC applies to, because players suffer from a lot of scrutiny and currently you can even get a VAC ban for joining a custom achievement server in CoD:mw2. 300 games currently have VAC implemented and it's unfair to a player that gets one ban to be possibly scrutinized from the players of all these games.
tl;dr it's saturday night and I bothered to write all this. AMA.