Consider *[calumnies](http://en.wiktionary.org/wiki/calumnies#English)*.  A *[calumny](http://en.wiktionary.org/wiki/calumny#Noun)* is a  “falsification or misrepresentation intended to disparage or discredit another” or  “false charges brought about to tarnish another's reputation or standing”.  Related words include *[obloquy](http://en.wiktionary.org/wiki/obloquy#Noun)*, *[aspersion](http://en.wiktionary.org/wiki/aspersion#Noun)*, *[slander](http://en.wiktionary.org/wiki/slander#Noun)*, *[defamation](http://en.wiktionary.org/wiki/defamation#Noun)*, *[slur](http://en.wiktionary.org/wiki/slur#Noun)*, etc.

*Edit:* In the context of filling in a word for the latter part of  “Stop giving «Negative ideas without any reason»” one might say “Stop giving *evasions*”, although that's a bit clumsy and a native speaker is more likely to say “Stop evading the question”, “Stop giving excuses”, or  “Stop caviling”.