Its kinda gray area. You can as long as you not afk ( doing something else while your chatacter autoattacks everything).
If you see bunch of em autoattacking in one place just report for botting, and let anet to sort em out.
One thing i wish anet would implement so that if you report someone you woukd get notification if they took action or if they found that it does not break tos... Some feedback, like in overwatch.