Should all victimless crimes be legalized in the us?:
I don't think there are any victimless crimes, by definition. We might ask why particular laws are enacted, because they seemingly don't hurt an individual, group, or society as a whole. But you have to look at the full effect of the action to determine if there is harm to society.

For example, prostitution should probably be legalized and regulated, as in many European countries. However, some aspects, such as working a street corner, cause harm to a neighborhood, and should remain illegal. Requiring them to work only in licensed brothels would be appropriate.

Similar considerations would apply to other 'victimless' crimes.