I have no desire or reason to visit Paris or other cities like it that are unfriendly to me.
I understand the "when in Rome" idea of blending in, but if I'm going to be harassed and in danger of being robbed I will pick another destination to spend my time and money
General alertness will keep you from getting robbed, and blending in a bit makes you less obvious as a tourist who is clueless. The 16 year old girls are Gypsies, literally, the French call them "Rums". One will come up to you and distract you. It is very effective if you are not aware of what is happening. I'd guess it's happened to me 5-6 times. I just keep walking, but my first trip over it distracted me, and the wife jerked me away and explained, which is what I'm trying to do here.
I think understanding such things makes a visit nicer, and mostly avoids bad things happening. You aren't in any physical danger, but you can lose a wallet. Oh yeah, don't buy those things that hang around your neck and let them dangle outside your shirt.
The other cities like Lyon and Strasbourg and Bordeaux are very different in that they have MANY fewer folks trying to rob you so visibly, I can't even remember any. I'm sure they have some pickpocket types. Paris is the tourist mecca so it attracts those who prey on tourists, and the police do not care at all about property crime. That is why every domicile in cities in France have serious security.
Our French friends and cousins who visit were amazed at our house in Cincy which had no fence or wall around it. They asked me how we could be secure in our house given we had a large green belt behind the house and anyone could sneak up on us.
I just said "Americans tend to have guns."