Restrictive in that it controls how you must license derivative works and release source code. It imposes an ideology on others.
> This is like saying laws against slavery restrict freedom (freedom to own slaves).
No, really, it's absolutely nothing like saying that, and if you care about free software (however defined, but in particular along the lines RMS endorses), you should stop using such a fantastically stupid analogy.
(Incidentally, this is comparable to restricting the freedom to enslave; it is a restriction on restriction.)
If you think the GPL somehow "imposes an ideology on others" but literally any other license does not, I am curious as to how. (Hint: a license cannot "impose an ideology"; if you do not agree, you are free to avoid it and stick with BSD code, or whatever else might suit your fancy.)
Your options are at least as:
1) acquire a licence of some commercial library, 2) use library with different open source licence, 3) develop your own library.
Your options there are similar, acquire a license for a commercial book (that you like), hit Project Gutenberg for an open source book, or write your own book...
If I had to guess, I would suspect that your real issue is that you do not find the things being restricted to be comparable (i.e., human life/will vs. the use of software), rather than believing that the comparison is somehow invalid for other reasons.
Second of all, it is highly debated wheter the restrictions imposed by the GPL are a worthwhile tradeoff; while noone in their right mind claims anybody has a right to own slaves...
And lastly, by comparing the GPL to laws against slavery you are trying to evoke certain associations, much like stallman uses the word swindle instead of kindle -- those are just cheap tricks that distract and make fruitful discussions hard.