malware bytes good or bad on Mac

Hi,

Good. It is widely accepted as safe to use on a Mac. Other malware apps install things on your Mac and slow things down and may interfere with proper operation, but Malwarebytes does not do any of those things. I use the free version and just manually scan periodically. Very easy and fast. It's the only malware app I've ever used.

Is is good for its' intended usage

The The Built in Security  is all that is required to protect the computer.

Should “ Certain & Specific Software “ referenced from above be installed - it will negatively impact macOS. It is suggested, to download directly from a respected ASC Contributor, the application Malwarebytes for Mac. 

It is free or paid for added features. 

Run the Application and it should remove the malware / adware. Once done, restart computer and test.