Like come into the city? People aren't necessarily riding gondoliers. These are all independent businesses pricing things according to their own interests (as they can and should). The stated problem is that there are too many people coming in so they are directly addressing that behavior.
It is legitimate to tax consumption of goods and services, e.g. make gondolieres pay an extra 10 Euros of taxes per trip. It is not legitimate to tax people based on race, sex, or country of origin - in fact, the entry fee scheme probably violates European Law, if unevenly applied (e.g. residents are not forced to pay).
See also: the German "foreigner's toll road" scheme.
Like come into the city? People aren't necessarily riding gondoliers. These are all independent businesses pricing things according to their own interests (as they can and should). The stated problem is that there are too many people coming in so they are directly addressing that behavior.