What is Straw man fallacy?

The straw man of logic does not scare anyone. No self-respecting crow would even rustle a feather at him; he is too easy to knock down. Precisely. The straw man is made incredibly easy to knock down so that when you are unable to refute your opponent’s argument, you can topple the straw man instead. The straw man is, in short, a misrepresentation of your opponent’s position, created by you for the express purpose of being knocked down.

We should liberalize the laws on marijuana.
'No. Any society with unrestricted access to drugs loses its work ethic and goes only for immediate gratification. '
(Down he goes! The proposal was to liberalize marijuana laws, but 'unrestricted access to drugs' makes a much less stable target.)

Traditionally, the straw man is set up as a deliberate over-statement of an opponent’s position. Many views are easier to argue against if they are taken to extremes. If your opponent will not make himself an extremist, you can oblige with a straw man. Any easily opposed misrepresentation will serve as your dummy.
The straw man is fallacious because he says nothing about the real argument. Like the ignorati elenchi society he belongs to, he is totally beside the point. His function is to elicit, by the ease of his demolition, a scorn which can be directed at the real figure he represents.

Aficionados of the straw man ploy reserve their loudest olés for those whose straw construction is concealed by a layer of flesh. The point is that the straw man does not always have to be created specially. By deliberately picking on a weak or absurd supporter of the opposition, and choosing to refute him instead of the main protagonist, you indulge in the true connoisseur’s use of the straw man.

Even today, applause can be gained for ‘refuting’ the theory of evolution, so long as one is careful to refute Darwin. Modern evolutionary theory is more advanced, having knowledge of things such as genetics to help it along. But you can set up Darwin as a straw man and, by knocking him down, give the impression you have ‘refuted’ the theory of evolution.

It is standard practice at elections to choose the most foolish or ignorant spokesman for the other side to deal with, as well as to fabricate extremists who can be felled with a scornful half-line.

How can we support the Democrats when one of their own union backers publicly advocates a 'worker state' like Soviet Russia was?
(Biff! Bam! And another straw man bites the dust. Union leaders on one side, like businessmen on the other side, can be politically naïve, and make much better targets than the slippery eels who lead the parties.)

Historically, the role of the straw man has been to show the dangers of change. A handful of reformers or radicals advocating greater liberty or greater tolerance have been trampled to death by legion upon legion of straw men in serried ranks calling for anarchy, licence, the destruction of society and the slaughter of the innocents.

Use of the straw man is fun. Everyone needs a victory or two for purposes of morale. If real ones are nowhere to be had, then walloping the occasional straw man can be most invigorating. In addition to the advice already given, you would be wise to con-struct and demolish your straw man, wherever possible, after your opponent has uttered his last word on the subject. Your straw man looks pretty silly lying in the dust if your adversary is there to disown him. If your opponent is absent, or has finished his piece, there will be no one to deny that the crumpled figure lying at your feet is indeed the opponent you were facing, rather than a dried-grass dummy, hastily fabricated to take the fall in his place.