Yeah. It is. When someone does the Nazi salute in public, they are telling you who they are, and you should believe them.

The previous sentiment goes for anyone. When they clearly tell you, through actions not words, who they are, you would be wise to believe them. It is extremely rare that someone intentionally acts against their own personal interests at the time of their actions. They may unknowingly do so, such as by voting for Nazis, but rarely do they do so intentionally.