Lomed Mkol Adam: Insecurity (whether it’s the same as low self esteem or not is debatable) may be a contributing factor in triggering abusive behavior, but I’ll bet that there are hundreds if not thousands insecure (Yiddishe) people who are not the slightest bit abusive. To become abusive, there must be a very rotten core of Middos Raos (character flaws) in their proverbial closet, where they can be kept very well hidden until after the Chasunah. What to do about this? See my earlier remarks from HaRav Chatzkel Levenstain ZT”L – working through one’s Middos via assidous Mussar learning, is a good start (with the help of a Rov/Rebbitzen).
Re therapy – many people are not aware or willing to face their flaws before marriage and would not classify themselves (nor would their friends) as aggressive, and so, according to your plan (very commendable though), they would never go for therapy prior to marriage, only to have unrefined (poor) Middos come out of their proverbial closet when things become not so much fun in marriage. Then they resort to abusive (or somewhat abusive) behavior against their spouse. So sending only “aggressive” ones to pre-marital therapy, is at best a small Yeshuah. We need to encourage our Chinuch Mosdos and individual mentors to help teens and pre-marital young adults really work on their hidden flaws (Middos Raos) through Mussar. No doubt that people could benefit from a healthy dose of therapy (although I am not certain if they should go for therapy when they start dating and/or bring their Chosson/Kallah into therapy after engagement, or even before they start dating) to help them really work out their hidden flawed Middos. I am sure this is oversimplification, but it is a start to tackle a nasty problem that every parent fears their child might be victimized by after the Chasunah.