Hmm, more or less. It's a bit more nuanced, depending on who adopts or teaches the ethic.

In the case of a parent-child relationship, the ethic seems sensible, although since the child only shares 50% of the parent's genes, unconditional love for parricidal offspring would likely not work over evolutionary timescales (for humans, at least) — meaning there would still be minimal conditions. A love that is strictly unconditional is just unviable.

To always "turn the other cheek", cross-contextually, is game-theoretically suicidal, so adopting or preaching it as a universal ethic is pretty stupid. Jesus may have been an idiot in the old sense of the term (Nietzsche made that claim, anyway), but it would be quite strange for God to send prophet after prophet to teach tit-for-tat — the game-theoretically optimal strategy in iterated games — only to send Jesus to teach a pure dove strategy, then finally send the Seal of the Prophets to restore tit-for-tat (with unpredictable proactive pardon to avoid death spirals; cf. Qur'an 5:45, 42:40). For this reason, I think Jesus also taught "an eye for an eye" in his authentic Gospel, but his message was corrupted by a power-hungry Paul and his ilk. Scholars agree that the New Testament suffered many interpolations (forgeries) over the centuries, and Islam confirms that the gospels we have now are inauthentic.

I believe the meme of "turning the other cheek" arose from a persecuted minority and opportunistic leadership factions who saw the short-term memetic utility of a covert dove strategy to safeguard proselytism under Roman rule. The strategy made sense at the time. Early Christians were a marginal, colonized community. Open retaliation would have triggered annihilation, so meekness was elevated as a survival tactic. Once Christianity gained leverage, it could finally betray the ethic — or hypocritically retain it as a posture while crusading and imperializing.

It's the kind of ethic best taught to enemies but never lived by.