Could the phenomenon of de individuation instead of lowering inhibitions actually infuse extra strength into one's weakness?Could that be the reason for the sudden impulsive and violent behavior?
Your question accurately mentions that de-individuation tends to de-activate or lower one's usual inhibitions due to the safety one feels as a member of a group. This is evident in people who belong to gangs, sects, even church groups. If they are sufficiently enmeshed and immersed within the group, they begin to BE the group and lose all of their individual mannerisms, preferences, and characteristics to adopt those of the group.
In the process of losing one's individual tendencies and adopting collective tendencies, one sets aside what is naturally inherent and known in order to give place to the new behaviors (this is true of many other learning processes such as second language acquisition, or even learning to dance!).
However, in the process of de-individuation there is a risk of repression, that is, of unconsciously putting off our body's and brain's natural signals that protect us, alert us, or even regulate our mood and behaviors. This does not mean that de-indivuation makes our weaknesses stronger, but that it drives the individual away from satisfying their natural psychological needs. This is what may lead to sudden outbursts of violent behavior, and the other forms of behaviors that show that a person has been repressed for a long time.