I think you could be overreacting. It depends upon the composition of your compost and the quality of the soil that was added to the compost pile.
Humus is an end product of compost.
Mulch can be any material you want to use to contain the moisture in soil. Plastic sheeting can be mulch. Bottle caps, rocks, ground up tires, you name it... it can be mulch.
Organic material decomposed would be compost. Leaves, small twigs, logs, grass, orange peels, horse manure, broccoli, zucchini. Your aiming at a 25:1 carbon to nitrogen ratio. Grass clipping alone won't do it, well. You need dry straw to dilute out wet fruit, etc... when piled up heat is created with the decomposition. Temperatures get pretty high in the center of the pile, helping to break stuff down, and sterilize weed seeds.
Is adding soil to compost bad? What do you do with your compost? Add it to your soil? If he added a large volume of soil then certainly it will dilute out the nutrients but it doesn't "ruin" the compost, the nutrients are still there, just not as concentrated. Would I want soil dumped in my compost? Certainly not. But ideally it is best dug into the top soil...Making all the soil a bit more fluffy.
Don't dig the crap out of your compost, that's the best part of it.
Have hubby go get a truck load or two of horse manure and mix it all together.