Is it considered backbiting for someone to say of a Quranic memorizer who commits sins, disobeys his father, and talks to girls: "He is a memorizer of the Quran, but he does not apply all that he memorizes"?

The Prophet, peace and blessings be upon him, mentioned that backbiting is "your mentioning your brother with what he dislikes." If what you said is true about him, then you have backbited him. If it is not true about him, then you have slandered him. Therefore, your friend has committed forbidden backbiting, and he should be advised and reminded of its prohibition and seriousness.