As much as squirrel hunters irk me during deer season, I have found that their presence is not an automatic death sentence to a spot. I'll give a couple of examples.
My very first hunt on public land. I went into a spot before daylight on opening day that I pre-scouted during the summer and then a few days prior to the opener. I had found a red oak dropping heavily along a shallow creek with good cover all around. It wasn't too far off the road, but having not seen any sign of hunter activity I decided that this was going to be my opening morning sit. I got settled in about 18 feet up a smaller red oak overlooking the drip line of the big red with all the sign under it.
About 8 am the silence of the woods was shattered by a shotgun blast not 75 yards off to my right front. It jarred me it was so unexpected. Then another shot rang out. This was followed by some voices, then rustling thought the woods, then a few more shots. I followed the sounds of the two guys through the woods in front of me but never saw them. They had worked through, shot up the woods and left. They were gone by 8:30. At this point I was pretty ticked off. I also was thinking "is this what public land is going to be like?".
I decided to sit it out, however, and after a while I was calmed down enjoying the woods again when I noticed two deer emerge from a privet thicket about 70 yards to my left front along the creek. They eventually worked their way in and I put an arrow through one under that red oak. I think those deer knew darn well where those squirrel hunters were before they ever got close, hunkered down while they were there and waited for them to pass on, just like I did. Shotgun blasts aside, if my feeble human senses let me follow those guys through the woods without ever seeing them then, what more could a deer or two sense?
Another example of squirrel hunting pressure not hurting a spot was a little valley on the old club I was in. This happened about three years prior to the above story. I went in to a little hardwood draw/valley before daylight and set up over a smoking hot white oak in my Summit climber. About 9 am I see to bucks walking parallel to me about 80 yards out. They are not headed my way, just passing through. Knowing they would soon be out of my life, I let out a doe bleat. Nothing. I let out a second bleat, this time about twice as loud. Nothing. Finally, in desperation I let out a very loud "MEHHHHH!". They stopped, looked up toward where I was, and headed strait to me like they were on a string. I arrowed the biggest one and his skull mount hangs behind me on the wall as I type this story.
Well, upon telling my hunting buddy the story and him asking where I killed the buck, he proceeds to tell me he was squirrel hunting that valley the evening before and shot about a dozen 12 gauges shells off in there and thoroughly tromped the place down. I'm sure he scented it up terribly too.
So, I don't write off a spot just becasue the tree rat shooters are off in there from time to time. The deer know they are there and know when they come and go and feed around them. Sometimes it's at night, sometimes it's right after they leave.