Is the western man being oppressed when he has to wear a tie and suit to the office in order to keep his job?

Suits are expensive and unnecessary. Some people (i.e. autistic) might have sensory difficulties when they wear them. If someone is vegan, most suits aren't so it further restricts what they can wear and they have to worry more about differences in look due to the stricter dress code. Fortunately, being restricted only while working certain jobs isn't as bad as being restricted in all public spaces.

Do we free him from this oppression by ostracizing him or making it illegal for wearing a tie?

No