Many Junker (and other) players were and are "worried" about the Harvesters. Here is the official "Junker Congress" view of Harvesters. The Harvesters are an "invasive species" in Junker society. Wanting or not wanting them is irrelevant...they are here now. Fortunately, Harvester and Junker Congress faction development began almost on the same day and immediately collided with one another as both the Congress and Harvesters had begun with the same ZOIs and interests. At that time, the Harvesters outgunned the Junkers in every way and negotiation was the only option. In typical Junker fashion, Junkers negotiated a situation that was disadvantageous to them into one that was advantageous. For this reason, Junkers need take no responsibility for Harvester action as they are fully autonomous faction of their own and can also rely on Harvester defense if attacked by other groups while Harvesters are present. In return, Harvesters receive basing rights and guarantees of non-Hostility by Congress members. Speaker Tinkerbell has the distinction of "knowing" the first Harvester and having dialogued with it since its arrival in Liberty. As a result, a level of "logical" trust has developed between Harvesters and the Congress. So long as that logic and predictability holds, the arrangement remains mutually beneficial. This is little different than the relationship maintained by Junkers with the Outcasts and Corsairs. Essentially, "Do what thou wilt and cause no harm" to Junkers. Having a relationships with the Harvesters is akin to having nuclear weapons. The risks and advantages are understood and never taken for granted but the advantages are used to the Congress (and Junkers) benefit. It is simple, pragmatic reality and "status quo" that makes the relationship viable and the Congress will seek to maintain that in order to eliminate Harvester risk and maintain the benefits of the alliance with them.
The agreement with Harvesters by the Junker Congress provides exclusion from attack by Harvesters so long as Junkers do not attack Harvesters. We are not obligated to defend Harvesters nor take sides in their conflicts--any more than we take sides in dealing with Outcasts and Corsairs. We also will not act to defend Junkers who willfully attack Harvesters for reason other than self defense from an unprovoked attack. If at any time either party violates these terms intentionally, the relationship and terms will be reassessed.
Also while you are at it read the rest of that page to better understand what the Junkers Congress stands for. As long as the Junkers congress and Harvesters have this agreement we WILL NOT attack each other. Sorry for you having to be on your own in that fight.
Edit: I agree with Tenacity. It is best to just stay away from Yanagi until Neutrality is brought there again. In the recent events it is pretty unsafe for anyone to be going there. I myself have also been avoiding it recently