Re: SEMRush Bot seen on results LOG files
They are visiting your site to document for their tools, not adsense. SEMrush is a reporting software that helps monitor keyword performance for organic ranking and paid search. They are one of the better companies out there to help understand site performance.
I've used both SEMrush and SpyFu, and never had a problem with them. If you block all bots from your site, then hopefully you have developed some internal/proprietary software for your own use. Otherwise you're going to have a tough time understanding the full market landscape.