Re: OP. "Unkind" word? Your lucky you didn't have to pick it up off the floor. If you don't want to tip, that's fine. They'll get along fine without your tip. But, they are not in any way obligated to have to listen to anyone at all who wants to address them with "unkind" remarks.
As to "ingrates..." is that merely an assumption or is it based in fact?
Now, as to tipping. I tip. I've got no complaints with tipping. This isn't old europe. Tipping is the norm for most restaurants. Given that most fast-food restaurants pay minimum wage, it is not unreasonable that tipping would be expected. If a tip make the meal to expensive, then one cannot afford to eat out. So, there are sandwiches at home. Absolute bare bones minimum is 15% at the very least with 20% the norm for good service. Again, if the tip makes the meal to expensive, one can't really afford to eat out.
Tips for fast food workers? It is no different than Walmart or any other business paying their employees minimum wage... and then giving those employees directions on how to access various welfare programs, etc. These companies pay the minimum and expect the taxpayer to subsidize their business operation. It is the same with companies that want to move into a area and expect to be cut slack on taxes in return for locating in that area, i.e., they want the tax payer to subsidize their operation. At least with the tips for fast food workers the people paying the subsidy are the ones actually receiving the product/service rendered. It would be appropriate to speak with the owner of the fast food restaurant and ask them why they are not paying a better wage to their employees. Once upon a time baggers at grocery stores were tipped. Then that custom went away as the grocery stores began to pay more than minimum wage. Cool.