As the times changes, some things never change.
Were there brutal, unchivalrous knights? Sure. Were there chivalrous, honorable knights? Sure.
Are there good cops today? Yep. Are there cops who plant evidence, abuse suspects, and make the rest of the force look bad? Yep.
Both people of authority, and keepers of peace. Just centuries apart.
I believe the same is said of samurai; some were brutal and tormented peasants in order to collect pay for their liege (daimyo), some tormented for fun, some were loyal and honorable and strictly followed bushido (roughly japanese chivalry).
It's all in who you pick to look up to. If you aspire to be like the chivalrous knights, don't let the renegade ones sour your vision. In the end, the goal isn't so much to be exactly like them, but to be become who you want to be by following their example.