It seems to me that in order to have Tourism revenue, you must have tourists. When a Canadian crosses into the U.S with his car to purchase some groceries or to gamble at Las Vegas, the U.S does not declare war on Canada. Purchases without visits are commerce, those with physical visits are tourism.
Un-armed ships should not provoke an armed response from the host civilization. They should be necessary for that civ to get any tourism revenue at the cost of the visiting civilization. So the equivalent of cars, yachts, civilian flights, are good for the economy even star bases which enable such tourism. A Tank, an Aircraft Carrier, a Fighter jet is another story.
If you are on bad terms with that civilization (I noticed there are many levels: warm, comfortable, ambivalent, angry, furious). The host civilization could charge an additional visa fee.
