That's valid - and Lisbon is an extreme, and heartbreaking example. It's been a victim of its own beauty. It's also extremely compact, making all the central real estate wildly more expensive. There's an unavoidable truth to the fact that when everyone wants to go to a place - often because of its local charm and reputation as a "real" living, walkable city (an anachronism in America) - prices go up, local people are displaced, and the place turns into a gentrified theme park, a shadow of what it once was. It's happening here in Portland. I saw it in Granada. Prague is a desperate example. I don't have an answer for it. I personally draw the line at allowing normal apartment units to be used as one- or two-night hotel rooms. Prior to Airbnb, short term furnished rentals existed but generally had to be sought through local property management companies, and the incentives for landlords still favored finding tenants who would stay as long as possible, if only because the scheduling and turnover system was so much less efficient.
Bottom line: I don't think it's necessarily destructive for people to go live in a foreign place, get to know the culture and try it out for the mid- to long-term. But I think that's in a wholly different category from tourists who use airbnb in lieu of hotels. And the tourist contingent is orders of magnitude larger and more disruptive to cities than long-term nomads who tend to spread out.
Just for instance; when we lived in Saigon, we lived way out in District 5. In Bangkok we lived in On Nut, at that time the end of the sky train. In both places we were the only farang we would normally see unless we went to the tourist areas for some reason. And in Europe, we lived mainly in villages of a few thousand people, not in cities. When staying somewhere for a few nights or even a few weeks, we stayed in hotels, not airbnb (I'm personally not comfortable with staying in airbnb's short-term because I don't like being in someone's private space, don't trust the quality, don't want to deal with individual landlords' rules and quirks, am wary of hidden cameras, etc., but that's just me).
There's no winning as a nomad, it's true. But I think most of us are keenly aware that we don't want to contribute to the destruction of the places we visit and live, and in fact tend not to cluster in the touristic town centers where housing is already scarce.