I completely understand your distress! Squirrels are cute, but they can be nuisances that are sometimes hard to live with. However, there are a few things that you can do to make co-existence a little easier.
When it comes to guarding your bird feeders you have a few options. First you can purchase a squirrel proof feeder. These can be as simple as one with a baffle to block the squirrels from climbing onto the feeder or more high-tech where the perch of the feeder rapidly rotates when triggered by the weight of the squirrel.
Where you position your feeder will also help. Bird feeders should be placed at least 6 feet from a jumping off point such as tree limbs, power lines, fences, and rooftops.
Another option is to fill your feeder with safflower seeds. Squirrels hate the taste of it.
To further reinforce these steps you can set up a squirrel feeding station with some of the foods they like to eat such as corn and sunflower seeds. If you start feeding the squirrels, you need to know they can be big eaters. One squirrel can finish off an ear of corn in a day. So whatever you feed them, make sure you have plenty on hand.
An additional benefit to providing squirrels with their own food supply is that it will keep them out of your garden and away from newly planted bulbs and flowers.
It also helps to add a few plants to your flower borders that have a strong astringent fragrance such as artemisia or santolina.
And if that doesn't keep them away, trying spraying the plants they are particularly fond of with a hot pepper spray. You can either purchase this from a garden center or make a batch at home. To make hot pepper spray simply puree two large cayenne peppers in a blender or food processor. Strain the puree to remove any seeds or solids. Add the strained puree to 1 gallon of water. When you are ready to spray, dilute 1/4 cup of the hot pepper concentrate with 1 gallon of water. To help the spray adhere to leaves also add about 1/4 tablespoon of dishwashing soap. When working with hot peppers it is important to wear gloves and keep your hands away from your face and eyes.
As with any spray, before you apply your hot pepper mix make sure your plants are well hydrated and test a small area before spraying the entire plant.