Children these days spend a lot of time using interactive media which increases their exposure to aggressive contents.

It’s difficult to imagine contents behaving aggressively:

Take a look at some examples of sentences using content (uncountable) and contents (plural countable). Remember that when you’re talking about something that can be countable or uncountable, and if you are writing in general or more abstract terms about that thing, then you should use the uncountable form.

• Children these days spend a lot of time using interactive media which increases their exposure to aggressive content.