I can't speak for a TV, but I rotate my PC Monitor.  Just for space considferation, I took the outer casing off of my monitor (there is an inner metal casing on mine).  If I could have I would have removed that too just to make it easier to mount, but after trying to do that a few times I gave up because there was almost no way of doing it without damaging the guts of the monitor.  As for spinning it without a degauss...  Similar to taking the case off, I tried getting to the degauss buttin to hack into it so I could attach a button to the top of the cab to press when turning it.  It was so impacted into the guts of the monitor, I would have had to remove that metal case to get to it.  So what I do will probably work for you... what I do is I have the montior hooked up to it's own power supply (which is then plugged into the main power strip for everything else - so when everything else turns on, the monitor does too).  When it is time to spin it I press the power button just for the monitor to turn it off and then spin it with the power to the monitor off (I have a button on the top of the cab just for this monitor).  Then when it is in place I power it back up.  At least on a monitor, it goes through a degauss on power up so all is well.  Again, I'm not a TV expert, maybe this isn't even necessary.  As for hurting the TV/monitor - I am sure it can't be the best thing for it, and the longer you leave it off after spinning it the better I assume.  Normally I try to only spin it once during a playing session to cut my damage chances down.