Originally Posted by Eggplant Jeff
I've never known the glycol or silicone brake fluids to have any detrimental effect on rubber. Oil-based products definitely can though (motor oil, transmission/power steering fluid, household oil, etc).
Just an FYI, automatic transmission fluid does not have any detrimental effect on rubber or polymers; in fact, it's critical that it does not. It is considered a "Safe" lubricant where contact with rubber or plastic is possible, such as inside a modern automatic transmission.