are ad hackers ethical?

https://londonist.com/london/features/could-london-ever-be-an-ad-free-city

This article talks about 'ad-hackers', people who remove ads from public spaces to replace it with art, bringing colour and life to the public space without actually trying to sell us anything.

In 2005, the average commuter was exposed to more than 130 adverts featuring more than 80 different products in a 45-minute London Underground journey; this rose to 3,500 commercial messages over the course of a day. 

These statistics are so high, but imagine how much higher they are now, 14 years later? We are already bombarded with adverts on social media, and when you consider that people are most likely to be browsing the internet in the comfort of their own home, it could be said that consumerism and advertisements invade the private sphere as well as the public sphere. While you can put an ad blocker on your browser online, you can't do that in real life. Perhaps 'ad-hackers' can be seen as an ad blocker for real life.