One of the biggest misconceptions they have for Goku is the fact that they only used Lifting Strength to compare the two, not both Lifting AND Striking Strength, which is 2 completely different things(You can't tell me that Goku needed Super Saiyan to lift 4 tons, yet blew through king kai's planet effortlessly with a single punch against Beerus). We've seen plenty of times a single punch between any fighter after awhile being able to create massive shockwaves with ease despite ONLY using their Striking Strength.
The other is with the fact that they also ignored one thing that any DBZ fan is still debating: That Super Perfect Cell was capable of destroying a Solar System. The issue isn't whether it's true or false(because it's been stated numerous times through anime, manga(original language and translations) and video games and even a video game outright confirms this even harder by showing off HOW Cell's attack would have destroyed the Solar System(Source of where all of it's at:
http://www.screwattack.com/news/cell-solar-system-buster-0) and the actual attack itself:
https://www.youtube.com/watch?v=B6MlSurcqR4)
If we put that into account, then Goku being BEYOND Super Saiyan 2 Gohan(who was still strong enough to STOP IT despite losing an arm) and now being SSJGod, Goku should be beyond simply being able to destroy stars and solar systems himself. Also, God Ki that Beerus and Whis have is stated to be VERY different than normal Ki by leagues so if we put it in that context(as well as even using say Xenoverse as an example where Beerus and Goku no sells Demigra's mind control technique because they are god level), that means Superman's main defence against Goku is now null and void(since you can stretch to say it's not magic which Superman is vunerable to).