Winston says this because he wants to live in a different Oceania with a different government. But to achieve this in a country of orthodox people who will only support the Party, there must be people who are impure and wicked (in the eyes of the Party) so that they can make a change. Julia brings Winston renewed hope because she is corrupt and not under the influence of the controlling Party. In the world of 1984, only the corrupted people can go against the Party to start a revolution. This is why Winston wants everyone to be ruined, dishonest, and unorthodox because they will be the ones rebelling and destroying the cruel system of the Party.
Winston isn't actually referring to things we would consider corrupt. He lives in a world where children and other family members turn each other in..... if they were "corrupt to their bones" in the way Winston means it..... families would turn on one another. The family unit would be the priority. Think of this in the exact opposite context of what you iniitially surmised.
I believe it is merely asking you to write down what the images remind you of. Like, maybe a childhood memory or something that happened recently or long ago. or maybe something you have seen :)
