If you don't keep logs, and someone has evidence you did something wrong, then there won't be any opposing evidence that you were in the right. So the jury will start out siding against you, and you won't have any way to win them back.
In fact if a judge thinks you didn't keep logs because you were afraid they would incriminate you, then they will tell the jury to consider the lack of logs as further evidence against you.
This isn't a prosecution, and nobody is alleging a crime. This is a civil lawsuit.
In a civil lawsuit, the standard of evidence is much different. You do not have to "prove" things beyond a reasonable doubt like in a criminal trial. The jury is instructed to weigh the evidence like a balance, and whichever side has the best evidence wins. Even if it's only a small difference that only slightly favors one side, they win.
That's why it's so important to have evidence that counters whatever the other side claims. You are bound to lose if your opponents are the only ones offering evidence on their side of the balance.
Agree. I believe I acknowledged that in my last sentence.
My point is a frivolous claim is a thing , and someone bringing a claim must suffice a basic level of evidence to even proceed. Indeed, as you say, "judgement" is at a lower final standard in a civil suit.