Further, saying that all people are low-level force users diminishes the relevance of Jedi and their opposites.
And saying that one's ability to resist is not based on willpower but latent force use diminishes individual importance as well because they succeed because of factors outside of themselves.
And ironically this statement is coming from the same guy (Dragon) who said he appreciates the "mystique" of the force.
You keep mistaking "Force user" for "person with Force potential". Force users use the Force.

People can have a low-level
sensitivity (which would manifest, for example, in "hunches" people have from time to time) without actually being able to consciously use the Force. They can still interact with it, however. "Will of the Force" isn't something that only the select few are involved in. Indeed, this is presumably why Force powers work on people in first place. You couldn't "mind trick" an inanimate object, or a droid (though there probably are alternate techniques for dealing with those), simply because they're not alive and thus don't have this connection to the Force.
It's been stated multiple times that all life has a connection to the Force. IIRC, Obi Wan said it in ANH (when explaining it to Luke), Qui-gon in TPM (that one was quoted a few posts back) and it might have been mentioned in TFH as well.
Actual Force users are special in that their connection to the Force is much stronger, thus enabling them to actually ask (or demand, in case of darksiders) something from the Force, as opposed to taking what it gives them. This is what "using the Force" is. Resisting mental probing is probably as far as using the Force goes for normal people, and even that probably doesn't go any further than blocking out the intrusion, even for the strongest-willed individual. It also seems like a very instinctive thing (boiling down to "not wanting to tell anything, very strongly"), see how Rey was able to turn the tables on Kylo during the interrogation and get into
his mind not only without even the slightest bit of training, but by a complete accident. Some species are even completely immune, presumably by their instinctive "mind trick defense" being much stronger.
Indeed, it seems not to work more often than it does. Notably, both cases when it does are stormtroopers. Military training puts a lot of emphasis on obeying orders first and thinking later (ideally during carrying the order out and not long after that...

). It probably makes the troopers prone to falling for the mind trick. Making a weak mind is easier than making a strong but obedient one.
To be fair in ANH when Ben uses the Force to "not the droids your looking for" past the checkpoint he states: "The Force can have a strong influence on the weak-minded." not the low on parasites. 
It would make sense that you need strong will to call upon your Force connection in first place, however small. A weak minded person wouldn't even think about resisting. Also, any "regular" use of the Force seems to be based on strength of one's mind as well. See the scene in which Luke is trying to pull the X-Wing out of the swamp.