Final answer:
The source does not directly state what Roubieu considered the worst part of being a graffiti artist, but looking at the life of the graffiti artist Basquiat, we can surmise that one of the significant challenges might be the health risks associated with the graffiti artist lifestyle.
Step-by-step explanation:
The question refers to the sentiments of graffiti artists regarding the challenges they face in practicing their art. While the source provided does not specifically quote what Roubieu said, it does give us insights into the life and struggles of a famous graffiti artist of the 80s, Jean-Michel Basquiat, also known as SAMO. Basquiat faced many challenges, including societal rejection for being a black, young, untrained artist and dealing with drugs that were prevalent during the time. His statement regarding art does not directly mention the worst part of being a graffiti artist but through his storied life including issues with drugs, one could argue the health risks associated with the lifestyle could be considered one of the worst parts.
Graffiti art is a form of expression with political and societal statements; however, it is met with opposition from those who view it as a crime or visual pollution. Despite this, artists continue to use this medium to call for action, raise awareness, and express their views, taking on the risks it involves, including legal consequences and personal health.