1- comparing meytrosexuals to homosexuals is like comparing professional women to lesbians
#2- metrosexual term may be new but the concept has existed in different cultures at different times, dandy in europe just a few hundred years ao, same for bankay in india.
overdone anything is ridiculous, whether it is a man taking care of himself, or whether it is desi ladies whining that they have nothing to wear because they have worn their $800 outfit three times and people have seen them in it. extremes are bad in any case. guys being so focused on clothing and themselves that its vanity at the expense of everything else is def not right but sadly the way it goes is that this extreme vanity is being defined as metrosexual and then that term is set to encompass any guy who bothers to use moisturizer and wears trousers that are teh right length and fit well and polishes his shoes 
However, the practice of men caring about their wellbeing, their quarters, their clothing, and themselves is nothing new, and stretches back to ancient civilisations.
btw, what is considered a “metrosexual” in US is considered quite normal in europe.