That's not true. I'm all in favour of our beloved eponymous usage, but the earliest known occurrence of "hacker" did have to do with breaking into forbidden systems.
http://duartes.org/gustavo/blog/post/first-recorded-usage-of...
http://duartes.org/gustavo/blog/post/first-recorded-usage-of...
http://tmrc.mit.edu/hackers-ref.html
Wow, I had no idea it went this far back. I've always been curious about etymology. After seeing this whole thread, I dug up these references:
http://www.cs.berkeley.edu/~bh/hacker.html
http://www.techrepublic.com/blog/security/hackers-and-cracke...
What's proven is that by 1963, people were writing "hacker" to mean "security breaker". To insist this is a perversion is rather silly when the "perversion" occurs so early and is in fact the earliest citation.
It seems likely the two usages are coeval. The benign one is how hackers saw themselves and the malicious one is how they were perceived by authorities.