Its doesn't tarnish Roma's reputation. That sort of thing happens every week...part of the Italian game.
Just like when "tifosi scendono in piazza" it all part of the Italian game...different strokes for different folks my friend. And you shouldn't be ashamed of what your most faithful supporters do.
You only have to see who Roma were playing to realise that it was a simple attack on the hardcore following of Hajduk Split, who don't exactly have a saints reputation now do they. Ultras vs Ultras simple as that.