Famous physicist fallacy?

Person A asserts something as true because a famous physicist said it.
Arguendo, whether or not it is true, the assertion is about the famous physicist's saying it.
Person B, who disagrees with A, says:
1. the famous physicist is a known troll, so what he says is just nonsense
2. the famous physicist is paid by x to say these things, so....
3. the famous physicist is not known for [subset of physics], but [other subset of physics], so.....
4. the famous physicist is known for physics, but the issue is another named science, so....
5. the famous physicist is known for physics, but the issue is another named topic, so....
6. the famous physicist is retired, so....

Both Person A and Person B are using fallacious reasoning, imo, but in rhetoric, what choice is there?

======================================
[edit] Person B only stopped b/c his keyboard broke...;)
[edit 2] an answer uses several versions... www.quora.com/Why-do-famo. . .

Ultimately, it's a false choice because it's not about the famous physicist (Transfer Fallacy) or his or her shortcomings (ad hominem credibility). It's about the veracity of the claim.

For instance: Referring to his own theory of a Cosmological Constant, Einstein was swayed by evidence and changed his mind - calling it, 'My biggest blunder'.

A famous physicist said it so it must be true: the theory of a Cosmological Constant was a colossal blunder.

No, in fact, it wasn't a blunder at all but largely correct. It's just not caused by anti-gravity within the universe, but by the gravitational forces of matter outside our finite spherical universe within an infinite space.