The comment above is criticizing the argument: the argument is "My ideas are being unfairly dismissed by the scientific community," and a valid counterargument is "No, your ideas are being fairly dismissed by the scientific community."
Yes, an obvious implication of that counterargument is "The person making the argument is the sort of person who publishes ideas that are regularly dismissed by the scientific community," but the strength of the counterargument does not rest on discrediting the speaker as a person - it rests on directly refuting the claim being made.
Or, in other words, if I were making the argument "Prof. Loeb's ideas are being unfairly dismissed by the scientific community," the exact same counterargument could be made against my argument. The fundamental reason an ad hominem is fallacious is that an argument's validity doesn't depend on who's making it. In this case, the argument is equally prone to refutation regardless of who's making it.