When I was teaching in the 1990's the staffroom was for teaching staff only. Later, teaching assistants and others were allowed in or invited themselves. The teachers tacitly understood the rules of living together and all was pretty harmonious. However, problems started later when others arrived and did not know 'the rules'. One incident stood out when they found the atmosphere quiet and boring and tried to play loud pop music. They found out very quickly that they did not want to listen to the music of others, for example, loud opera - or test match commentary. The idea was that no one could impose their personal taste on a public place so everyone had to be restrained in public.
The same applies in this case. The defacing of the bungalow wall has been committed to people who do not understand the dire consequences of everyone else indulging their cacophanous tastes as well as themselves. They would not like what others could do and they certainly wouldn't like it if every style and oddity were placed adjacent to each other.
This chaos is what planning laws, parish regulations and street plans are meant to prevent.
These bungalow dwellers have not the wit and imagination to see where it would lead were others as selfish as themselves. Someone ought to point it out.
And yes, despite the optomistic comments posted on this thread to the contrary, these people are demolishing the value of the surrounding properties by their self centred actions.