They probably do this because they believe that facts are not subject to disagreement. Therefore, by getting you to uncritically accept what they say as fact, they hope that you'll concur without further thought. 

Let's see if I can clarify this. 

There are 10 kinds of assertions, but only one of them is factual. And by “assertion,” I mean a string of words implying the truth of something. They are fact, agreement, inference, judgment, phantom assertion, insight, pass-through, opinion, gossip, and asininity. 

A fact expresses the truth of something that can be confirmed either by testing or by experiment replicatable by others. For example: “If you fall out of an airplane over an open field, you'll hit the ground.” That's a fact. 

An agreement purports to express the truth of something simply because people are of one mind on the subject. To illustrate: “A touchdown in football is worth 6 points.” Now that's not a fact; it's an agreement. 

An inference purports to express the truth of something on the basis of careful observation followed by careful reasoning. For example: “The universe began with a Big Bang.” That's not a fact, either; it's an inference. 

A judgment purports to express the truth of something based upon observation and experience. To illustrate: "Look at those clouds. It's going to rain soon." That's not a fact; it's a judgment. 

A phantom assertion purports to express the truth of something based upon nothing more than a string of generally acceptable words relating to a specific subject which has little or nothing to do with the real world. As an example, “Inflation is an increase in the volume of money and credit relative to available goods resulting in a substantial and continuing rise in the general price level.” Or “The latest Hinkum-Dinkum poll shows that 42.6% of Americans have lustful thoughts from time to time. The poll has a margin of error of plus or minus 4 points.”

An insight purports to express the truth of something based upon what appears to be a sudden illumination, a flash, an intuition, a hunch — i.e., something that just seems to pop into your head. Example: “No man is ever defeated who emerges from conflict with his soul unstained, and no man is ever victorious who does not.” Now that's not a fact; it's an insight. 

A pass-through purports to express the truth of something based upon nothing more than its repeated appearance in print or in some form of electronic data. It may also show up in a specific discipline or field of study as a “fact.” For example, “Columbus discovered America in 1492.” That's not a fact; it's a pass through. 

An opinion purports to express the truth of something based upon nothing more than personal likes or dislikes. As an example: “Jim Brown was the greatest running back ever.” That's not a fact; it's an opinion. 

Gossip purports to express the truth of something based upon nothing more than idle chatter or groundless rumor. For example: “Charlie Smith is cheating on his wife.” 

And an asininity is a statement, generally statistical, but it needn’t be, that’s completely inoperational, meaning that there isn’t a single reasonable or logical procedure or operation that could allow for the reaching of such a conclusion or for the testing of it. There are countless asininities out there. Here are just two of them, the first statistical, the second not: 

“There were 12% more blackbirds in California this year than the year before.” 

“Secondhand smoke kills.” 

Given all that, the next time someone starts an assertion with the words “It's a fact that . . . .” or “The fact of the matter is . . . .” listen very carefully to what follows. The chances are that it will be anything but a fact. 

Oh, by the way, what I just said was not a fact; it was a cross between an inference and a judgment. 

Think about it.