1. Close Android File Transfer
2. Open Activity Monitor and kill “Android File Transfer Agent”
3. Go to /Applications/Android File Transfer.app
4. Click and select “Show package contents”
5. Go to Contents/Resources
6. Rename “Android File Transfer Agent” to “Android File Transfer Agent_DISABLED”
7. Open terminal and rename“/Users/username/Library/Application Support/Google/Android File Transfer” to Android File Transfer Agent_DISABLED.
Reference: https://gist.github.com/zeroseis/ce66d4c6b776577442a6