Popular opinion is that if the oil is too high, the crankshaft whips it up producing a froth (full of air bubbles) that gets sucked into the oil system instead of just (incompressible, pure) liquid oil. This froth (being full of air) is compressible, and you both lose oil pressure and lubrication in the critical spots in the engine -- i.e., parts like cam lobes become oil starved.

It's best to remove the excess oil -- you might be able to do that through the dipstick tube using a variety of suction devices (hand pumped and electrical pumped), commonly sold in chandleries (boating supply stores), to change the oil in inboard marine engines. These engines commonly have a sump drain that can't be reached (in the bilge), so the accepted technique is to suck the old oil out of the dipstick tube -- these devices have a long, narrow tube for that purpose.

Interestingly, this is also the proper technique in Mercedes-Benz dealer service departments for their engines -- although it does work in my old M-Bs (M110, M201 and M203 engines), it doesn't completely work in the Volvo (red block) engine -- there's some obstruction that prevents the inserted tube from going all the way down, like in the MBs. But it should get far enough down to suck out the top 1/2 qt or so.
This is a lot easier than opening the drain plug, right? :-)

Good luck.