This line of thought peaked in the 90s and continues today. I believe there is a subgroup of patients with a variety of CNS disorders (including ALS) that have a greater ratio of immune-mediated symptoms than others, possibly in part because of environmental exposure.
The "devilish detail" is identifying that subgroup, and individualizing treatment when an exacerbating organism is elusive. Beware of "one size fits all" protocols that can do more harm than good, not to mention some of the, well, cults that have grown up around the antifungal/antibacterial paradigm. Moreover, in the vast majority of cases, a complete cure or remission is not achievable at this point.
In any case, the strongest possible general health is also important in immune-mediated illness.
Best,
Laurie