"And the sprinkler of the waters of sprinkling shall wash his clothing": Scripture here distinguishes between water which is sufficient for sprinkling and water which is not sufficient for sprinkling, the first rendering a man tamei to render his garments tamei; the second rendering a man tamei to render foods and drinks tamei. You say that this is the intent of the verse, but perhaps its intent is to distinguish between the sprinkler and the toucher (of the water); the sprinkler who does not touch rendering his garments unclean, and the sprinkler who touches, not rendering his garments unclean?
Now does it not follow (otherwise) a fortiori, viz.: If the sprinkler who does not touch renders his garments unclean, how much more so the sprinkler who touches! — But perhaps the intent is to distinguish between the clean and the unclean? — Would you say that? It follows a fortiori (otherwise), viz.: If the clean one (who touches it) becomes unclean, how much more so, the unclean one! — But perhaps the intent is to distinguish between those who are fit (to sprinkle) and those who are unfit? — Would you say that?
It follows a fortiori (otherwise), viz.: If the fit one becomes unclean, how much more so, the unfit one! You must perforce accept the first supposition — Scripture here distinguishes between water which is sufficient for sprinkling and water which is not sufficient for sprinkling, the first rendering a man tamei to render his garments tamei; the second rendering a man tamei to render foods and drinks tamei.