It's one of many variants which pre-date the adoption of the symbol by NSDAP. It's not even very similar in form, unlike, say, the American version worn by Escadrille Lafayette, among others. If people can't tell the difference, that's a function of the stupidity of the observer, not that of the person who painted it on his bike.
If people can recognised it as a swastika, then it's probably not a good thing to have displayed openly in the first place on account of, y'know, the recent history.
It's 70 years ago, people need to get over it. Not to mention that Stalin on his own, leaving other Soviet leaders out of it, murdered more people than Hitler, and people don't get on their high horse about people displaying the actual flag of the 1930s Soviet Union as retro chic.
It's one of many variants which pre-date the adoption of the symbol by NSDAP. It's not even very similar in form, unlike, say, the American version worn by Escadrille Lafayette, among others. If people can't tell the difference, that's a function of the stupidity of the observer, not that of the person who painted it on his bike.