What was the opinion of Hitler regarding pornography?
A little research reveals that Nazi party policy on sexuality was somewhat contradictory. This is not surprising, the same thing happened in many fields. Hitler's views were presumably similar to those of the party that followed him.
The core of Nazi policy was the idea of "race" and its fundamental importance to everything. An individual's own body was not their own to do with as they wished, but belonged to the German race. Nichole Loroff's article on Gender and Sexuality in Nazi Germany seems reasonably thorough.
Like most authoritarian groups, the Nazis espoused social conservatism, and wanted people to stay in very traditional gender roles, with men dominating society. Motherhood was viewed as the most important activity for women, serving the race in an equivalence of the way men served it as soldiers. However, they didn't try to hide and deny sexuality, but to turn it to their ends in increasing the population.
So "artistic" female nudity was a major aspect of Nazi art, while unapproved art with sexual elements was automatically pornography and "degenerate art." Unmarried German girls were encouraged to have sex with men, which caused large numbers of pregnancies - seen as a good thing - and spread venereal diseases - covered up, or blamed on the women.
Overall, the policy was an incoherent mixture of social traditionalism and satisfying the desires of men at the expense of women. Katherine Burdekin's novel Swastika Night dealt with it rather effectively in 1937.
In "Mein Kampf," Hitler railed that
"The black-haired Jewish youth lies in wait for hours on end, satanically glaring at and spying on the unsuspicious girl whom he plans to seduce, adulterating her blood and removing her from the bosom of her own people. The Jew uses every possible means to undermine the racial foundations of a subjugated people." (Book 1 Chap 11)
Thinking as he did, Hitler probably believed that pornography was an instrument for leading German people, particularly women, "astray" (verfuhren).