Vandalism

Nope.

It may "feel" like a victimless crime. But (a) the graffittier doesn't own the place s/he's defacing and (more importantly) (b ) quality of life crimes and misdemeanors tend to contribute to people's overall feeling of chaos and that a city's government just doesn't give a damn. They can feel a city is a dangerous place, and that they are vulnerable. As a result, it can contribute to families moving out.

See: https://www.ncjrs.gov/pdffiles1/photocopy/167807NCJRS.pdf (page 5 et seq) and
https://www1.nyc.gov/assets/oignypd/downloads/pdf/Quality-of-Life-Report-2010-2015.pdf (on page 2, footnote 1)

From the latter: "...police activities like educating people about quality-of-life regulations, creating partnerships with community members and organizations, conducting graffiti clean-up programs, and enhancing lighting or closing parks. These tactics, commonly characterized as situational crime prevention or problem-oriented policing strategies, may be more effective at reducing disorder than issuing summonses or making arrests..."

Also, there hasn't been a causal link made between quality of life arrests and felonies. See: https://www.seattletimes.com/nation-world/report-no-link-between-quality-of-life-crimes-felonies/

So the answer isn't necessarily to arrest people or issue summonses and I'm not advocating tossing someone in the slammer for tagging a building, even one which isn't scheduled for immediate demolition.

Rather, considering that community efforts seem to work best, then by tagging a building, even a condemned one, it can seem as if the tagger is actively trying to undermine the efforts of the community.

And if the community as a whole starts thinking the city government doesn't care anymore, then it can result in entire neighborhoods dying out.