For example, I don't trust Microsoft. We now know that they have some kind of backdoor in Skype. They are able to give the contents of my conversations to law enforcement or intelligence agencies. If I'm targeted, they can just flip a switch and record anything they want. But that doesn't mean it's impossible to have secure conversations if you use a Microsoft OS. It's unlikely that there is an actual remote admin backdoor in Windows itself, and even if it was, you'd have to be targeted, your PC identified, and the backdoor has to be activated before someone can siphon off data. And if you have a decently secure network, and use secure, open source software that doesn't route your traffic over microsoft's servers, it's much much harder to identify, let alone eavesdrop on you.
The existence of one highly specific access vector does not imply that the whole platform is compromised. Conversely, just because there is the theoretical possibility that the platform may be compromized on a low level, one should not forego additional security measures.
Just because the NSA might install a camera above my keyboard, I shouldn't stop encrypting my emails. Just because Intel might subvert my CPU in multiple ways doesn't mean I shouldn't be wary of them introduce specific potential security weaknesses.
*) Let's look at a potental tinfoil-hat attack mode. Intel might have some entity in their processors that detects whether I'm a potential target for surveillance and then weakens the hardware crypto. It would have to be pretty clever to find out from the CPU instructions that I'm doing something suspicious, or that I'm visiting a website containing a secret "enable weak crypto" byte sequence. While we're at it, it might also rewrite instructions to weaken 'software' crypto too, or even inject instructions to phone home. While theoretically possible, I believe this is highly unlikely. It is much, much more likely that they'd introduce a subtle weakness in the RNG that would let them crack keys a bit easier.
Being afraid about the former surely is paranoia, being afraid about the latter is rational distrust in a black box, IMHO.