Definitely not California but literally the first part of traffic law in Germany says that caution and consideration are required from all partaking in traffic.
Right- but the "consideration" here is the person merging onto the highway actually paying attention and adjusting, rather than pointedly not even looking (this is a very common merging behavior where I life). Changing lanes isn't without risk even on a clear day with good visibility. Seems like my suggestion of slowing down or speeding up makes perfect sense because it's less risky overall, and is still being considerate.
Note that I personally do change lanes at times when it's safe, convenient, I am experienced with the intersection, and the merging driver is being especially unaware.
Note that I personally do change lanes at times when it's safe, convenient, I am experienced with the intersection, and the merging driver is being especially unaware.