I actually want to point a couple things out:
Firstly, network cards aren't typically configured to have access to the rest
of the system. Simply encrypt your data, and a network card running non-libre
software can't do anything with it. If anything, your ISP is likely to be
more of a threat to your privacy than proprietary software in a network card.
Secondly, firmware only runs on certain devices. If you don't have those
devices that require proprietary firmware blobs on your computer, the blobs
won't run anywhere. For instance, if I were to run Tails on my laptop, none
of the proprietary software included on it would run.
Also, Tails doesn't use a kernel that was not deblobbed; it uses Debian's
kernel, which is deblobbed, but also ships blobs, effectively adding these
blobs back in. I'm not entirely sure, but I think it's likely that it only
distributes the blobs needed by network cards, not blobs for full GPU
support, since they added these blobs in on purpose specifically to make sure
the system would be useful for as many people as possible (their reasoning
probably being that a system designed to access the Internet anonymously is
kind of useless if you don't have Internet access).
I want to note that I don't endorse Tails; it would be great if someone would
do a similar live system that we could endorse. But I think some are
exaggerating the potential damage to privacy caused by non-libre firmware
blobs.
