It doesn't imply that. It says that (some) capitalist states build walls to keep refugees out (like the US and in a way the EU) while (some) communist states build walls to keep (potential) refugees in (like the GDR)
Agreed. And the (probably unintended) irony is that the Berlin Wall was ostensibly built in order to keep the capitalists out. Be careful what you wish for, especially when it's a wall. They work both ways.
You don't really believe the propaganda of the "Antifaschistischer Schutzwall". The wall was always to keep GDR citizens in.
Nobody ever had the intention to keep capitalists out.