Why adware/spyware; these programs are viri!

What is so different about a company writing malicious code to get their site visitors or get their company revenue without the consent of the computer owner? The people who make these programs sicken me; they must terrorize innocent people with their VIRUSES! This is malicious script it shuts down anti virus and anti adware in some cases it even tries to disable firewalls so it can do its dirty work. I am sick of getting this crap on my computer taking my lowering my systems speed and making me waste time fixing what it has done to my computer. These are not some harmless pop ups anymore the adware industry's programs have manifested into a much bigger problem, evolving to elude being removed by the most trusted software (adware aware, spy bot S&D). These programs have even been known to spread like viruses do. Is this not legally questionable behavior for a program to install without your notice and not have any means of removal? From my view these are viruses...not some harmless adware in your cookie folder that tracks your surfing habits it has become much worse.