"Hindutva" as defined by Savarkar baguely means Indian nationalism that draws its 'inspiration' from Hindu/Maratha culture. It cant be called Hindu extremism is broadest sense, largely since Hindu fundamentalism is an oxymoron moreover, founding fathers of Hindutva were Agnostic Hindus. Hindutva rose as a complementary movement to Marathi cultural resurgence (all founders were Marathis (specifically Marathas and Konkanastha Brahmins and till 1970's most memebers of RSS were Marathis). Hindutva in these days is a vague ideology. It differs from one propounded by Savarkar to the one practised by 'parties' like Shiv Sena and Bajrang Dal.

BTW I was an active HSS member till about 2003, before i left Hindutva for good.
©