I certainly agree that motorcycle oil is optimized for performance in a motorcycle, but I don't agree that means that non-motorcycle specific oil (car oil) is going to be harmful to the bike (i.e. accelerated wear).
I ride more than a lot of guys. There's now 101,000 miles on my 2014 S10. At 88,000 miles I had an oil analysis done. At that point, I had ridden the following distances using what would be called "car oil":
30,616 miles, O'Reilly Auto 10W-40
4,038 miles, Quaker State 10W-40
1841 miles, Valvoline 10W-40
22,864 miles, Rotella T4 15W-40
2,106 miles were with an oil that I forgot to record what brand it was.
With motorcycle specific oil:
9,973 miles. Yamalube 10W-40
17,527 miles, with Castrol GO 4T
So, up to 88,965 miles, 69% of them were ridden using "car oil". Blackstone Lab's report showed that wear metals were low next to averages, and their opinion was that the internal parts were getting along well.
I ride year round, and average about 11,000 miles per year. It gets hot here in summer (not like Texas hot, but hot), so riding conditions can be a little rough. I'm a pretty sedate rider; no bouncing off the rev limited, or popping wheelies. I change the oil often, sometimes even before it's due.
None of this proves anything, of course, other than as an anecdotal data point. But my own particular experience had shown me that using "car oil" in a bike (as long as it isn't energy conserving oil with friction modifiers) isn't a first class ticket to disaster.
And yep, when I changed the oil last week, I put Rotella T4 back in.