When a scientist speaks to the public, they represent (in much of the public's mind, anyway) all scientists in the field, and (arguably, to some extent) science

When a scientist speaks to the public, they represent (in much of the public's mind, anyway) all scientists in the field, and (arguably, to some extent) science and scientists in general. If they say anything wrong, then that harms the reputation of all of the above. From the perspective of a fellow scientist in the field, the speaker must (a) have made mistakes in his analysis, (b) have taken an approach to his analysis that was sloppy enough to allow such mistakes, and (c) have announced results despite having done an analysis that they should have known was sloppy. In other words, it demonstrates not just incompetence but negligence and a disregard for the truth. These are hateful qualities in a scientist. This is assuming the case of a scientist who confidently makes incorrect assertions. If they qualify what they're saying—"So far this is what the research says, but it's preliminary, there are a few other tests I'd like to see"—then that's a lot more defensible even if they're wrong. (There is a legendary tendency for reporters to remove all the qualifiers, but at least that's not the scientist's fault.) If they state everything confidently, more confidently than the evidence justifies, but they happen to be right on all their assertions so far, then that may be mildly irritating. If they're intellectually cautious and they're right, and if there are scientists that complain about these people, then that does sound like jealousy.