The main problem with SOPA is that it is not possible to solve a market problem with legislation. Copyright infringement is a market problem, and markets are a lot more effective in delivering solutions than Governments. Consequently, SOPA will utterly fail to prevent copyright infringement, resulting in even MORE draconian laws sometime in the future.
Specific to the problem of music and film is that these markets are highly regulated oligopolies that use their market power to engage in price fixing. Unlike efficient markets, in which there are a range of different prices, the music and film markets only have two prices: Idiotically expensive and free (illegal).
Personally, I would LOVE to pay $1 per episode to watch my favourite HBO series at a time, and in a place of my own choosing. Sadly I cannot. Hence, I either don't watch it at all, or I obtain it by 'other' means. Monopolies/oligopolies only offer one price, and they are free to gouge their customers as long as they can prevent any competition in the market.
In other words, SOPA is NOT about preventing piracy (because that is a hopeless cause, much like the war on drugs), but about protecting the music and film industries illegal, anti-competitive price fixing practices (by way of preventing any other production/distribution of that type of media). Illegal price fixing is a small price that all Governments will gladly pay, as music and film support the propaganda/mythology creation industry of Government.
The simplest solution to prevent piracy would be to open the music and film markets to competition, but that is exactly what the RIAA and MPAA are trying to prevent.