First, just to make a correction, ALA (Alpha Linolenic Acid)--the "parent" form of omega-3 is in NO way an antioxidant. It is an essential fatty acid and has certain anti-inflammatory properties....but it is actually quite extremely vulnerable to oxidation and without the presence of saturated fat (which serves to protect, transport and assists in utilization this delicate polyunsaturate) and ample vitamin E, it can readily peroxidize into a nasty free radical of its own.
But I digress....
Different antioxidants function differently in the body and tend to target only certain, specific free radicals (for instance, beta carotene is known to have a quenching effect on singlet oxygen free radicals and vitamin E focuses on almost exclusively peroxidized fats). The unique free radical chemistry of Miracle-Mineral-Supplement is, apparently, more singularly vulnerable to vitamin C.
My understanding is that it is best to wait "a few hours" after taking Miracle-Mineral-Supplement to introduce any appreciable amount of vitamin C. Some say after 3 or 4 hours is OK, some say 6 (mid-way between doses). Stands to reason.
I do not have enough information on the free radical nature of Miracle-Mineral-Supplement to know how inimical it may be to, say (for instance), things like polyunsaturates or LDL cholesterol (which is only problematic when peroxidized) in the body. Not knowing more, my default incliniation is to make sure my diet and supplementation is antioxidant-rich. I also use a transdermal glutathione cream (glutathione is poorly absorbed via the digestive tract) over vascular areas a couple of times a day to help off-set any potential glutathione depletion initiated by MMS. In addition, I consume extra high ORAC (Oxygen Radical Absorbance Capacity) green drinks and foods to help offset any risks. Just my own personal precaution.
I don't really think there's any major cause for alarm or hysteria here, just a reasonable level of precaution and discretion.