How about you look at it like this:
It was the 1st of April right? Well the video in and of itself was a April fools joke. However, Ug-Thak is an actual thing. Yes this Ug-Thak you just saw was a joke but me and @Sleepmaster (2 of the 4 remaining Borderlands Custom Content creators left on planet earth which are still actively making custom content for BL) are making a 5th "unofficial" DLC for the game of Borderlands. And we've already announced that Ug would be the raidboss for our DLC.
It was basically an idea of Sleep to raise more awareness for us custom content creators in general. As good as 90-95% of the BL community as a whole don't even know custom made stuff exists for Borderlands!
So how about you see the bigger picture here and try not to be upset by an April fools joke, but instead get a laugh out of it and realise that Borderlands is going to get a 5th DLC made for it which, might I add, will be indistinguishable from a DLC made by GBX. (We are VERY keen on proper detail, maybe more so then GBX itself seeing as we are not time/budget bound)