The glass mugs just had the logo and words painted on. I have several Old Spice mugs, both glass and ceramic. The ceramic ones all have the designs and words painted on under the glaze. The glass ones are all painted. Probably via some silkscreen type process.
It wouldn't be all that hard to scrap the paint off. It would take a little effort but wouldn't leave any marks unless you used something that actually gouged the glass. Why someone would remove the Old Spice words is open to lots of speculation. It could just be something as simple as the way the mugs was held in use or some loathing of the words Old Spice. Who knows, Old Spice may have had some demonic meaning to the previous owner.
It wouldn't be all that hard to scrap the paint off. It would take a little effort but wouldn't leave any marks unless you used something that actually gouged the glass. Why someone would remove the Old Spice words is open to lots of speculation. It could just be something as simple as the way the mugs was held in use or some loathing of the words Old Spice. Who knows, Old Spice may have had some demonic meaning to the previous owner.