Sorry but you are just posting generic 'the state is bad so everything it does is necessarily bad' tosh. The state decides general parameters - badly - and then uses the data to apply them. Refusing to take part will simply compound their failures and deliberate strategies. You are playing into their hands.
And it is not just 'the state' (which doesn't have an actual consciousness to decide these things) who offer these reasons, they are supported by workers in a vast range of industries.
Danny Dorling says:
Both the 1991 and 2001 census revealed that our admin records were including a million people who were not actually here anymore. The 2011 census found half a million extra people that were not here according to the official estimates. The census corrects and finds faults in admin records. Admin records are not a safe replacement for it.
Censuses have always been used to address the key problems of the day. The 1911 census asked women how many of their babies had died. Infant mortality at the time took up to 1 in 10 of the richest of peoples’ new-born infants. The 1971 census asked for details about housing quality, hot running water and toilets. Slums were still being cleared then and the authorities needed to know what was left that was still in poor condition. The 2011 census asked, for the first time ever, how many bedrooms were in every home. It revealed that there were more bedrooms in central London than people. It showed us that we have enough bedrooms to go round, but that we are increasingly sharing out space badly. In short the 2011 census reveals that the rich have been taking too much of our most limited resource: space.