"We never had a problem with this clause before, why would you want to change it?"

Oh do I hate this line. But it's a two-way street. I'm very fortunate that for one of my first freelance gigs, I read the contract and specifically pointed out that I would be using personal/open sourced code snippets, and that I might want to reuse/open source some of the code I produced for them (only snippets with general interest).

They agreed without a flinch, and thanks to that experience, I'm going to hold every other employer to the same standard "I never had a problem with this request with any other employer, why would you want to refuse?"