I'm not familiar with the literature and consensus on them being a Catholic concept, but I am sure they are not about using the enemy's weapon, at least in the sense that you're arguing.

They were created by the high elves and given to the kings of Númenor. The only rightful uses of them in LoTR is by Denethor and Aragorn.

I suppose it could be argued that the illegitimate use of them by Sauron and arguably also Saruman eventually factors in their downfall, and as such it is their use of the enemy's weapons which is fraught--in Saruman's case, that he gets corrupted (but I interpret him already vain and arrogant, and thus on a downward path even before).

In Sauron's case I think lies a nugget of what wisdom Tolkien hoped to confer, especially in his interaction with Pippin. The palantír invites speculation, in that it lets you see things but not all things. Sauron knows a little (the ring is with a Hobbit), is shown a little (here is a Hobbit in Saruman's stone) and in speculating draws wrong conclusions (this is the Hobbit I've been looking for!, etc).

His seeing Aragorn in the stone is different in that Aragorn is the rightful heir, has authority over the stones, and shows truth with intent, which scares Sauron, sends him in a panic and drives him to make foolish decisions.

So, while we are told about the danger of using the enemy's weapon, I'd argue it's from the opposite perspective, and also not quite whatever moral or other lesson Tolkien hoped to confer, rather I believe the moral of the story is to avoid speculation about what happens in another place, or time, and instead trust in yourself, follow your heart and do what is good.