I can't remember quite how I responded to that the first time I got it but it went something very much along these lines:
"To gain big you have to gamble big, if big gains were simple everyone would be doing them. There is always the possibility of failure, of losing everything you bring to the table, and being a hundred percent committed to anything, bringing everything you have to the table, is a bad gambling strategy. We can work together for our mutual benefit, but if you expect me to throw my entire life, and potentially all my future options, behind something that may or may not work out... well, I can see how that's to your benefit but I don't see how it's to my likely long-term good. The average lifespan of a company is thirty years, and significantly less in the startup space. I'm afraid that if you want me to sacrifice my interests for yours you either need to be paying me a lot more to justify the added risk you're asking me to take on, or we've reached a parting of the ways."
People like that are, I feel, just looking to take advantage of you. Loyalty is won by laying the best hearth, not demanded.