In university, my professor said that his position is that there are no qualia. He acknowledged that non-philosophers can find this position bizarre, but did not explain the rationale behind why he thought this. So what is the rationale behind this position?
The position is that of eliminative materialism, or of delusionism, relative to consciousness. The two are somewhat different.
Qualia are often cited by non-physicalists as direct evidence against physicalism. Many physicalists try to accommodate qualia and physicalism, and argue that the reasoning from qualia to non-physicalism is in error. For a committed physicalist who finds these arguments to be invalid, there is a problem:
IF one is convinced of the truth of physicalism, AND that the various efforts by philosophers to reconcile or explain qualia physically fail, THEN in order to continue to hold by physicalism, one must deny the reality/existence of qualia.
Note, this POV relies upon the presumption that physicalism is so well supported, that any apparent evidence against it must be an observational error.
This reasoning is rarely admitted to by its advocates. The only explicit statement of this reasoning process I have found was in Susan Blackmore's A Very Short Introduction to Consciousness. For Blackmore qualia was one of many observations or evidences about consciousness which she argued that physicalist explanations failed to explain/predict/accommodate. The accumulation of problems/failures, she considered provided a sufficient justification to depart from the more common physicalist view that consciousness is somehow an aspect of matter or processes, to the much less intuitive one that consciousness, and all the challenging data including "qualia" that are bundled with that term, does not actually exist.
Blackmore's excellent summary is only a summary. Works that spell out non-qualia/non-consciousness views in significantly more detail would include Consciousness Explained, by Daniel Dennett, The Engine of Reason The Seat of the Soul by Paul Churchland, and The Astonishing Hypothesis by Francis Crick. Crick and Churchland argue a reductionist eliminativism, in which they suppose that better and better neurological characterization of the brain will eventually remove any need to think about "consciousness" as opposed to specific neurological states. Dennett does not rely upon reduction, but instead takes a behaviorism/functionalism approach in which behavior can be explained physically, so the only issue is that the pesky internal experiences can't -- and his work presents mental frameworks to try to make his denial of internal experience more plausible to his readers.