Your three arguments can easily coexist, they are not exclusive of one another.
Agree. They could be all true, all false, or any combination. What do you think about each of them?
1- 'it was a perfect phone call, there was no quid pro quo'
2 - 'it's all hearsay and second hand information' (this implies that direct evidence would be relevant)
3 - 'even if he did do it, it's not impeachable'