Straw targets.

In arguments or discussions, I've found that it's almost always the case that the person making an argument - at any given point - misunderstands the point of view of the person they're arguing against.
As such, they're essentially making an argument against a figment of their own imagination. Which is often quite amusing.

They also seem to like doing the "one-size-fits-all" trick. Where the same illustration, or point, or argument is always brought in to what they say. If you're lucky, they might have two or three to vary it up a little.
Now, admittedly, sometimes that can be a good thing. Solidifies your perspective, gives it some common ground. Which is fine if that's good ground.
But if that ground's a bit shaky - then perhaps you'd better think again.

One of the many reasons I avoid arguments, and particularly online discussion boards and the like. They can be amusing at times, but they can also get nasty, confused and crazy; and often for simple misunderstandings.

Being able to walk in other people's shoes helps with these things. Quite a bit.