My point had nothing to do with whether a secondary was useful or not - I just wouldn;t recommend racking a beer that is actively fermenting. Its very possible you could stall the fermentation. Plus, if the primary fermenter is infected that means the beer is infected (which, just because a blow off went through the air lock doesn't mean this is the case at all) and I don't see what the logic would be to rack contaminated beer into a clean fermenter.
In other words: All that will be accomplished is moving the problem from one container to another.