Indeed, people tend to believe that there's an enemy out there, and will search for a name to put on it. If that enemy is disproven - satan is the grand example because, just as there's no solid proof for his existence, there's no solid proof against, so he can be a perennial enemy - people are more fearful than ever. The enemy isn't vanquished, or no longer a threat. Just, "If they're not my enemy, who is?"
In the USA at various times, the common enemy - with varying degrees of any real threat - has been, among others: Catholics, Protestants, Irish, Chinese, Japanese, blacks, Arabs, and "Islamic terrorists" (the latter, a blanket term so vague that, shortly after 9/11, some folks were attacking Seikh taxi drivers, neither knowing nor likely caring that Seikhs aren't Muslims.)
There are, incidentally, a handful of scattered Christians out there who don't believe in satan– or in original sin at all. It's an odd belief system, to be sure, and one most Christians would denounce, but it exists. I haven't seen much of it online, but I've spoken with a few of them.
Even funnier are some of the comments on the linked vid, like this one: "There is a very great deal of work being done to expose MK Ultra mind control on pop stars, including satanic ritual abuse, in order to shatter the core personality into multiples. The victim (in this case Katy Perry) would then have a handler (much being posted that Russel Brand was for a time Katy Perry's handler, while Jay-Z continues to be Beyonce's)."