How did him saying that "offense can play around Keledo easily" turn to "offensive pokemon can set up on Keledo"? Offensive teams usually have a SR user (not relevant to this discussion since Keledo isn't taking much), a couple of priority users and a pokemon that is either scarfed or can boost it speeds. Ideally you would lure Keledo out mid game and hit it with a priority or damage it indirectly or the enemy using it to tank a resisted STAB move used by you, but you even don't need that to happen. The common theme with all Keledo sets is that it's not running any bulky investment, any legitimate sweeper using its (SE or Neutral) STAB on Keledo will probably either OHKO it or damage it badly to the point a single priority hit will finish it off.
As for finding out what set Keledo is running, you only need to know whether or not it is scarfed. You scout that the same way you scout any other offensive sweeper. If it's scarfed, you bring out or save your scarfer to deal with it or set up with your LGS on any other pokemon, if it's not, any of your outspeeding pokemon can revenge kill it. Alakazam, Latios, Latias, Gengar, Starmie all maim it.
I'm only here to read posts about defensive teams and whether or not they are refusing to change to the meta or that Keledo is putting a strain on their team building options and forcing them to run ridiculous niche sets and whether or not his list of checks are/aren't real.
Defensive teams are fine against Keldeo, maybe the Specs or CM version can do some work in the hands of a good player but I think offensive teams really bear the burden. Anyways Rey said in his post that you're not playing against "a moron"; your example sounds like you're just outplaying the guy by keeping enough constant offensive pressure to play around Keldeo, if your only answer to Ebelt Keldeo is one of those 5 Pokemon then your team is going to take a lot of damage if a guy with Ebelt Keldeo ends up being the one who is playing better and you have to do the responding.