Yaakov was afraid that the Canaanim would gang up against Bnei Yaakov and go to war against them, and this is exactly what happened. The Medrashim are loaded with the war stories of Yaakov Avinu against the Canaanim. (see Ramban).
Despite Yaakov’s complaint against them, and despite his expressing his fears about potential wars, Shimon and Levi didn’t seem impressed. They just said: הַכְזוֹנָה יַעֲש ה א ת אֲחוֹת נוּ לד לא “Shall we allow our sister to be treated like Hefker?” They stood their ground even against their father! They felt that they did the right thing and all they cared about was the Kavod of their sister and they had Bitachon! (Me’am Lo’ez also says this).
And indeed, despite this story, it says later: וַיְהִּי חִּתַת אֱלֹקִּ ים עַל ה עָרִּ ים אֲש ר סְבִּיבוֹת יה ם וְלֹא רָדְ פוּ אַחֲר י בְּנ י יַעֲקֹב לה ה that the Canaani neighbors suddenly became petrified of Bnei Yaakov. This is the Schar of a Baal Bitachon; i.e., that Hashem causes his enemies to fear him.
I have seen this many times. I have a friend who is by nature very gentle and he has lots of respect; but also fear, fear of people. He was taught to become a macho personality. This was very much against his grain. But it worked wonders, and it helped him work on his own weaknesses. He once had a serious court case, but his fearlessness caused his enemies to fear him!
