Well to say it "protects" the system might be a stretch, I mean sure if the pressure keeps building and building something will blow out, probably a hose or compressor seals, but in the common sense, what it is there for is to keep the AC blowing cool air, it helps the heat exchange through the condensor so the vent temps will lower. So no, IMO there is no "danger" in disabling the low speed fan circuit, maybe in "danger" of having lousy AC performance is all, but again when the temps get hot you can reconnect whatever you decide to disconnect.
When the car is moving, I believe I heard 15mph or so, the aux fan isn't even neccesary, the air is moving through the condensor faster than the aux fan provides. It really is only beneficial when stopped in traffic.
I would consider the high speed circuit much more important than the low speed circuit, that system is there to keep the engine from overheating.

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