A mathematician might find his feelings engaged by certain questions. Sir Andrew Wiles was passionate about Fermat's Last Theorem from the age of about ten, I believe. (Say, by contrast, that he took little interest in statistics. Perhaps statistics even disgusts him.) Does any of this "corrupt the purity of the logic" of his (rather long) answer to the question how to prove Fermat's Theorem? No, it just powered his interest in mathematics. Besides, why isn't it possible to be inspired and motivated by a thought or an ideal? The ten-year old Wiles had the thought, 'I will prove the Theorem', and this motivated him and engaged his feelings - and the grown-up Wiles did prove the Theorem. The purity of his logic was perhaps even assisted by his passion.
I believe it was Hume who made the point that reason cannot motivate us, only our feelings can. Supposing that's true, I have a far-flung conclusion that seems to follow from that: when the panelists on this site choose which questions to answer, they're motivated by some emotion, not by reason. But doesn't this corrupt the purity of the logic of the answer? Perhaps not necessarily so, but isn't it likely that of the 2,600+ questions a good number have been tainted? How is it not the case?
In writing this answer I am motivated by the desire to help non-professional philosophers with their philosophical questions. That desire does not influence the answer that I give, it just motivates me to give some answer or another. Or: in writing this answer I am motivated by the desire to point out that emotions should not be thought of as ipso facto "irrational" or "unreasonable." That desire is connected with the answer I give, but may or may not have influenced it. Or: in writing this answer I am motivated by the desire to appear on this website. Again, that desire does not influence the answer that I give. Or: in writing this answer I am motivated by the desire to attack the philosophy of David Hume. That desire is connected with the answer I give, but may or may not have influenced it.