I had the same problem. In my case, the original event had been deleted from iPhoto on my Macbook Pro.
1. I physically attached my iPad to my Macbook Pro.
2. In iPhoto, I selected one photograph and made it into a new event using the exact title of the event on the iPad.
3. I switched to the iTunes application on my Macbook Pro. Under Photos I selected the check boxes to sync photos on the laptop with the iPad, to sync selected photos and under Events, I selected the new event I just created. I applied the changes and performed a sync. At this point, the event on the iPad went from having over 300 photos to just one.
4. Back on the Macbook Pro, under iTunes, I deselcted the box that would sync the iPad with any photos on the laptop. I was prompted whether I wanted to remove the previously synced photos and I indicated I did. I ran another sync and the event was now completely gone from my iPad.
Hope this works for you too.
I have found an easier way
Step 1: plug in device
Step 2: click on the dice which popped up in iTunes
Step 3: Go to Finder and Create a new folder and do not pun nothing in it.
Step 4: Click on the "Choose photos from" tab and look for the new folder you created
Step 5: Click sync and your " my mac photos" album will be deleted
This exact issue was driving me nuts as well. But I finally figured out how to do it.
Before you start, be sure to close the "Photos" application on your device.
1. Plug in your device (in my case it is the iPhone) to your computer.
2. Open iTunes and select your device.
3. Select the "Photos" tab for your device.
4. On the upper right side (below "Sync Photos from …"), you will see a list where there are options.
5. Highlighted should be "Selected albums, Event, and Faces, and automatically include …" This is where you select "no Events"
6. Sync your device and the events will be gone.
If you meant on your phone, I recently had the same issue. I could not delete any photos that were synced under the album 'Events From My Mac'.
I tried pressing random buttons, and found a solution. (this is for photos only. it will make your photos deletable, have the same date and location, and not be under events from my mac).
First, I tapped on the photo I wanted to keep, and be able to delete. Then, I clicked on 'Edit'. Something will pop up saying something like 'This Photo Cannot Be Edited. Would You liked to duplicate it?' and then you have to click 'Duplicate'. after that you adjust something (the light, or color or whatever), and then adjust it back to normal. You will be able to tap 'Done' after that, and it will be in your camera roll! After that you are able to plug in your device into your computer and no longer need the events from mac any longer. Haha sorry if this confuses you.