I just read the commentary on pants being not Tzniut for women because they out line the shape of the legs and is immodest. If this is so should men not wear skirts, or very large pants so that their legs don’t show as well, as the shape of legs are immodest? After all, women also have a Yetzer Hara and men have legs too.
Although the halachic literature is more concerned with defining modest dress for women than for men, it is improper for a man to dress in a way which is provocative. Since trousers have been a common mode of masculine dress, it is not considered provocative by definition. In my opinion, an exposed chest, or shorts on a man on the street is a breach of modesty.