1) Anti 2) Denier 3) Refuser 4) Technophobe 1) Chronic pessimist 2) Contrarian 3) Cynic 4) Gloomy gus 5) Habitual denier 6) Nixer of suggestions 7) Obstructer 8) Obstructionist 9) Obstructor 10) Pessimist 11) Resister 12) Skeptical sort 13) Thwarter 14) User of bad language 15) Vocal pessimist 16) Vocal skeptic 17) Wet blanket 
[n] - someone with an aggressively negative attitude
noun someone with an aggressively negative attitude
a person who habitually expresses negative or pessimistic views: Despite a general feeling that things were going well, a few naysayers tried to cast gloom.