I can fully understand your situation and the way you feel about it because it has happened to me several times. I have been willing in the past to loan out tools because of the pressures of getting the job done when it would make it so much faster and easier to loan out the needed tool. Whenever I have borrowed someone's tool in the past, if I messed it up, I have always seen to replace it or make it up one way or another. Perhaps your frustration is coming from not expressing yourself to the borrower in such a way that they understand that "yes you can borrow my tool but if you break it, you replace it because it is money out of my pocket and food off my family's table." Maybe you need to use their need to borrow your tools to your advantage in letting them know that you value your tools and aren't a pushover. My suggestion would be to express yourself in a calm and rational way in order to get your point across in a serious way and then maybe they will realize that you mean business and will at least think about it when they are screwing you over. If you don't want to loan out any of your tools, have them show you want they need done and then do the job yourself. At least you would be getting paid for it and using your tools for the purpose you bought them for. There is no easy answer but I just thought I would add a few ideas that I have thought about before.
