Right now the UAW is trying to present a united front with the management of the Big 3 but under the surface is a bitter mutual dislike. The UAW sees management as being incompetent, overpaid, and quick to blame the union for its own failures. Management for its part is very bitter about the above market wages and benefits that the unions are able to extract for "unskilled labor" and union workers "inflexibility".
Building a car with competitive efficiency is a highly complex process involving careful design of both the car and the production process. Henry Ford and Walter Chrysler both had the ability to build a car from the ground up with their own hands. Such skills are rare, though, and both turned to masses of semi-skilled laborers, used in very carefully engineered ways, to build their cars. One of the essential points of such an arrangement is that employees are expected to be like the parts they assemble: interchangeable. The process is developed with the intention that any capable person could be placed in any position on the line and keep up. There are some more skilled positions (usually in maintenance and setup) that require more education and pay a little more but the principle holds.
Is it any wonder that people trained to think that a person is an interchangeable part would find the idea of a few people making a huge multiple of what everyone else makes absurd? Management would take the other side and argue that paying a worker nearly double what another worker off of the street would cost* is absurd.
For my wooden nickel, the workers have the better side of it. But then again this is a world where a great inner city school teacher makes far less than a mediocre backup quarterback in the NFL.
*The difference in cost is not so much the wages and benefits being paid to the person on the line, but in pensions and benefits being to retirees that are part of the contract with workers.