Multiboxers (especially the ones with a lot of accounts, I know a guy with like 40 accounts) are a tiny but visible minority in EVE and as such get scape-goated a lot. The last time CCP told us about this stuff, The average was less than 1.5 accounts per person and people with more than 10 accounts were like 0.1% of the population.
And yet the people who post about multiboxing act like everyone has 60 accounts stripping whole systems bare of rocks and rats every 10 minutes. The whole anti-multiboxing mentality seems to be driven by equal parts ignorance and jealousy.