If New York City in the post-Bloomberg era can still be called gritty, chaotic, artistic, and weird, the political demonstration in the Metropolitan Avenue subway station on Tuesday afternoon was a quintessential New York gathering. Kid Lucky, the “human beatbox,” was there. So was Matthew Silver, better known as the guy who dances on Astor Place in his underwear, swinging hula hoops and giant stuffed bananas while shouting slogans like “Put down your phones” and “Love is forever.” Other protesters included a rapper, a harmonica player in a bowler hat, an assortment of guitar-strumming singer-songwriter types, a mime, and Robert Cornegy, the seven-foot city council member from Bedford-Stuyvesant and an alumnus of the legendary 1984-85 St.