If the intent is to prevent the transmission of ideas, then yes it's censorship.
If the intent is to protect from harm -- totally unconnected to ideas -- then no it's not censorship.
The reason Defender deletes keygens is that they're statistically associated with malware and viruses, as any Google search will terrifyingly immediately reveal. It clearly is falling under the "protect from harm" category as it's designed to do.
But so to answer your question clearly: deleting "Animal Farm.txt" because of the ideas inside is censorship (prevents it being transmitted). The video game would similarly be censorship if based on its content. But if it's deleting all keygens, regardless of content of their associated video games, then clearly not censorship.