It's not so much weaseling, so much as whether the normal audience for this speech would have interpreted it as disclosing facts. You can't just say "in my opinion, this professor stabbed a student to death" to shield yourself from liability. But you can say "in my opinion, this professor stabbed a student to death, because I can see that they have the beady eyes of a criminal"; the basis for your claim is clearly not some undisclosed fact you've learned about the murder, but rather your weird ideas about facial features.