The amount of resources that most of these products use is higher than than most spyware.
And yet one of the first things I do on Windows boxes that are running slow is to do a simple cleaning. CCleaner is pretty good and it is free. Followed by install a few select programs. Even after the cleaning it is not uncommon to end up dumping a good amount of malware, viruses. Invariably once removed the machines are much faster. The actual overhead of most of these programs is minimal, often little more than the space used on the HD. This is because they are not active until activated for use. I usually even turn off the auto update features. It means you have to remember to update them, once a week is usually good enough.
The burden of running a Windows machine is that it is vulnerable to this sort of thing. And always will be. And IE cannot actually be entirely disabled if you're running a current Windows OS. You could do it in Win95, perhaps early incarnations of Win98, but it was subsequently integrated so it could be claimed to be 'part of the OS'. Thanks MS. You can restrain it and keep it from doing certain things but it is always there. An endless series of back doors that can never be entirely sealed shut.