What is Most Sinful ?

In the Seventh Canto Srila Prabhupada says that cutting down trees to print “unwanted literature” is the “greatest sinful act.” (Srimad Bhagavatam 7.2.12/purport) But in the purport to 9.2.3, he says this: “What then is to be said of sending cows to the slaughterhouse? This is the most sinful activity in human society.”