By that requires reasoning. And reasoning is not taught in school much anymore. Kids are not trained to ask questions anymore, but to prepare for standardized tests - where there is one right answer and everything else is wrong. Not a lot of room to question the premise of it all.
Fortunately, there is a simple way to figure out whether you are being indoctrinated or not. If someone presents you with an argument, and you start to ask questions and they try to shut you down, chances are, they are just trying to indoctrinate you into a belief system.
And it is not hard to shut down discussion. Using the leasing argument as an example, the salesman says something to you like, "If you lease this car, it will free up your cash flow!" If you ask him "What does that mean, exactly?" he might say something like, "Well, your monthly payment will be less, so you'll have more money to spend on other things!" And that might sound convincing, but if you ask, "But is the overall cost of leasing less than owning, or more?" and that's where he will hem and haw or just outright lie to you. You have to get out a paper and pencil and do the math yourself and see how the real numbers add up.
Sadly, most of this falls on deaf ears. We all want to believe what we want to believe. We want to believe that this outfit makes me look slimmer. We want to believe that our new smartphone plan is a "good deal". We want to believe that we pulled one over on the car salesman, or that our reward miles will get us a "free flight" to Duluth.
Frankly, if we really want something, we are willing to believe anything. So maybe the real answer is to want less, and then you will be less inclined to want to believe. Maybe.