It’s called common sense, not bias.
That's what everyone calls his own unsubstantiated, biased conjecture.
Since, after extensive investigations over the past 56 plus years, no credible evidence indicates LHO had an assistant helping him with his trip to Mexico City
And "credible" is used to disregard data that doesn't fit into one's unsubstantiated, biased conjecture. Like the surveillance photos of other men, and the imposter phone calls that the CIA recorded.
and there are several common everyday scenarios that would also explain this, it is extremely unlikely that the books’ return date on the cards is proof that he did (have an assistant).
There's nothing we actually know that makes this "extremely unlikely". The info from the library just says "return date".
And based on experiences in the past here in this forum, it is very unlikely that anyone will ever convince you of anything.
Perhaps if they came up with better evidence than "common sense"...