Surrealist tango evening in Leipzig

Love your third question!! It made me chuckle a little that you put that right up there with 2 extremely deep and thought-provoking questions...

For some strange reason Mondays in Leipzig are dedicated to demonstrations organized by a group of people who, according to their own definition, are against the islamification of Europe. Another group of people usually demonstrates on the same day against the first, and the police tries to avoid clashes between the two. It is a lot of work for the police force of the city, particularly in the summertime when there are also many tourists circulating in the centre.

Last Monday a musical group from Berlin was trying to perform Tango music under the statue of Bach in front of the church of St.Thomas. In the beginning all was going well but suddenly there was a lot of noise from the first group of demonstrators with their shaven heads, their german flags and their slogans. The noise became unbearable when the second group of demonstrators started playing some loud jazz music and shouting slogans against the former. The poor musicians continued with their programme and the supportive audience applauded more than they would have done under normal circumstances.

Regarding the above, I had a few questions:
1.Why are these people allowed to demonstrate almost every Monday of the year?
2.Why do extremes always look so alike, regardless of whether they belong to the far right or to the far left?
3.Why the Musical Ensemble didn't perform at least one piece by J.S.Bach?