First, two quick points of clarification. In general, this debate revolves more around the idea of UN peacekeepers being used in offensive roles (i.e. aggressive combat operations) versus more neutral roles (i.e. monitoring or distributing aid). Although there may be a case to eliminating the force entirely, there are some basic functions the UN must carry out that require manpower so for the sake of clarity I will frame this debate between having a large scale offensive Peacekeeping force versus a more neutral bare bones regiment. Second, given that the United Nations bases its charter on the preservation of individual rights one could make a deontological argument that any cases of assault by UN troops violates its own charter and therefore delegitimizes the entire organization. As such, proponents of this idea would want to remove peacekeepers entirely for this reason alone. I think there is a lot of merit to this idea but for a sake of contrast and realism I will entertain more utilitarian calculations of UN peacekeepers.
In theory, the role of UN peacekeepers, specifically in offensive roles, has its merits. Without agents of force, it is unclear how the UN can uphold its declarations; how would the UN arrest a victim of war crimes or protect a sacred area without troops? Moreover, UN troops can function to destroy dangerous militant groups and conduct combats raids on arms smugglers and human traffickers. Some would argue that individual countries can do all of these tasks themselves, especially considering they already supply the manpower in the current UN system anyway. Conversely, UN offensive interventions have their own unique benefits that can't be achieved by foreign troops alone. By operating under the UN flag it allows for some semblance of neutrality and objectivity that can't be obtained by letting countries (and all of their inherent biases and political goals) control the arrest of human rights violators.
Despite what skeptics may claim there is a large body of empirical work that these UN interventions save lives and promote regional stability. Havard Hegre of the University of Oslo finds that the use of offensive peacekeeping operations reduces the risk of major conflict relative to no conflict by more than 90%. Furthermore, the risk of civilian casualties is decreased. Kofi Nsia-Pepra in the Journal for Peace and conflict studies found that making missions more offensive by one standard deviation from the mean lowers intentional civilian killings by 31 percent. Logically there are a couple reasons why this could be the case. First the aforementioned impartially may allow the UN to be viewed more positively by occupants of the country. In doing so, actions that normally promote extremism like foreign occupation happen to a lesser extent. Second, the UN, being made up of over a hundred countries, has access to significantly more intelligence than any individual actor via collaboration. Lastly, as the UN needs multilateral support whenever it engages in offensive operations, this multilateralism can lead to regional actors providing support within the conflict area as opposed to ignoring it or working against the UN aims. Actors can still dissent from a UN decision but there are generally more multilateral elements of a UN intervention than a single country either acting unilaterally or trying to pursue multilateralism itself.
Although certain counter-narratives exist (namely the idea that offensive interventions may in fact degrade the UN's impartiality) UN peacekeepers provide some strategic advantages. From a strategy point of view, ruling them out as an option prevents us from realizing these benefits. Empirical data suggests that they can actually provide security particularly in issues that align with the core values of the UN like stopping civilian killings. To more fully realize its potential, I would double down on regulation and assault training so that we can enjoy the strategic benefits without having to swallow the atrocities that occur on the individual level when UN troops commit unnecessary violence.