If you have a windows system or virtual machine, you can insert your sd card there and search in explorer for ._ It will list all this files and you can mark them all and delete them all so you dont have to do it by hand.
Afterward use ftp on mac to tansfer files. Then it will not create those .files
Beside the already mentioned way to copy stuff to the SD-Card using ftp or scp You may use a small app on Your Mac that cleans the SD-Card on eject. I use https://www.macupdate.com/app/mac/52076/him for this purpose without any problems.