Otherwise your code can simply be co-opted to build platforms which are very much closed (see OSX/BSD).
In fact it should really be argued that GPL isn't good enough and you should be using AGPL which also gives rights to users who use the program on a networked basis.
The OP's question by the way, reminds me of this discussion http://news.ycombinator.com/item?id=3802516 , in which some argue against the GPL as "unfair" and ruining their day because it prevents usage in walled gardens (http://news.ycombinator.com/item?id=3803492).
Would it be more pragmatic to keep the discussion on HN going instead of developing evasive concepts?
A lot of GNU was replicating work that had been done by other Unixes but the goal was to have it available as GPL.
Next to that: I would only call it ideological if it was for some higher, intangible value in a future yet to discover. But I find the purpose of the GPL from inception until now only pragmatic.