Over 100 years ago, Pope St. Pius X wrote an encyclical about Modernism called Pascendi, and, strangely enough, he actually used the terms 'Modernism' and 'Modernists' quite frequently. Who would have thought?
Sure, there is nothing wrong with using the term of course.
It's the synthesis of all heresies and Benedict covered most all of them!
I just don't understand how it provides an excuse for blasphemers, heretics and apostates by saying they have some kind of mental illness where they believe they are one thing when in reality they are not.

In other words, they have apostatized by renouncing the faith and therefore have left the Church but still believe they are Catholic.

They are leading souls to Hell but believe they are "helping".

This gives them some sort of pass?
St John had a different name for somebody who denies the Incarnation and the Resurrection of Our Lord Jesus Christ:
"Who is a liar, but he who denieth that Jesus is the Christ? This is Antichrist, who denieth the Father, and the Son."
1 John 2:22