Dear sir, I usually use this website as a corpus-like point of reference and mostly don't have the time to comment or embark on any type of interpersonal interaction, let alone giving, gathering, abstaining from or indulging in points. Regarding your comments about the wrongfulness of this idiomatic sentence, schematized here in the form of For one to be trouble, I can assure you it is true. Your justification is not that sound and somewhat veiled, supported and benighted, by your relative eloquence. This expression is quite idiomatic, common and not that profound to cause, demand or get to be resolved by, any extra effort or scrutiny. The pop-cultural reference of the titular song I know you were trouble or an SNL skit were a feeble guy is known to be trouble, are other references, once again serious linguistic justifications as well as the fact that linguistic idiosyncrasy, even in the form of proposing ad hoc syntactic structures, let alone semantic propositions, is to be noted and of prime importance. So, that's that.
In addition, your choice as to take offence at -pardon me, but this phenomenon is at the moment so ubiquitous that I am just writing based upon statistics- or just absorb what I am proposing notwithstanding, I do believe that the mechanics of your writing is way over-embellished for a comment, which may imply, even though unwantedly, lack of strategic competence of non-native speakers to overwork lingual paradigms during their interaction as a means by which to orchestrate all sorts of internal and external equilibriums. God bless.