Although people who use 'decimate' do not usually mean 'to destroy one in ten', they do not usually mean 'annihilate', meaning 'to reduce to nothing' (Latin 'nihil'). They may, however, mean 'to destroy a large proportion' such as nine out of ten.

I am annoyed by people saying 'just because [...] doesn't mean ...', when what they should be saying is 'just because [...] it doesn't mean ...' or 'just because [...] that doesn't mean ...'.