Hi Dennis.  I do agree, from your second paragraph, that the Churchill quote may not be fully fair.  It was from a Commons address and those are always characterized by wit and one-upmanship.
I do think, however, that Leo (Pope, not brother) was pretty clear on socialism in Rerum:
"Hence, it is clear that the main tenet of socialism, community of goods, must be utterly rejected, since it only injures those whom it would seem meant to benefit, is directly contrary to the natural rights of mankind, and would introduce confusion and disorder into the commonweal. The first and most fundamental principle, therefore, if one would undertake to alleviate the condition of the masses, must be the inviolability of private property. "
If a "main tenet" it condemned, than the system upon which it is based cannot stand. This assumes, of course, that Leo's conception of "socialism" is the same as we understand it today.