The simple problem is that you need to warm up the fats sufficiently for it to spread. The same holds true for many other fatty spreads, like chevé or neufchâtel. You can get around this somewhat with two tricks:
- Place the knife you're going to be using to cut the pâté in a cup of hot water for a minute or two before slicing. Dry it off, then slice in. You may wish to warm it again between slices and/or spreading.
- Thinly slice the pâté. You'll have an easier time spreading two or three thin slices than one thick one.
Your other option is to let it warm up out of the fridge. I personally prefer not to leave the whole thing out, I just slice it, place it on the bread, then put the unused portion back in the fridge; I then let the sliced portion sit a little while before trying to spread it. (this works okay in the summer ... not so well in the winter with the way I heat my house)