a /an /the

Cuyber-bullying destroys (.....) harmony .
"the" definite article not needed.
Used to refer to a thing in general rather than a particular example
"harmony" is uncountable, abstract noun, not specific, not particular, refer to a group of thing described
The headline seems to be:-The less said about the whole thing on 'harmony', the happier it will be.Also "harmony" is a state of peaceful existence and agreement.It is the need to be in harmony with......To live together in perfect harmony----co-co-co-co.In social, racial harmony one cannot find the definite article "the".

a,an are indefinite articles used before uncountable nouns when these have an adjective in front of them.It is used to show that something is a member of a group; eg:-Their new car is a B&W--black&white. He's a teacher. She's a teacher.She is a little red riding hood.etc.

Three are three types of nouns that don't need an article:
1. proper noun
2. plural noun
3. mass noun (or uncountable noun)

"harmony" is uncountable, therefore no article is needed unless you want to describe a "specific" situation.