Protein is only bad for the liver and kidneys if your entire diet is high in protein. So the diets for losing weight by eating almost all protein work, but are bad for you. Just balance it out with veggies.
Cholesterol is a complicated and widely misunderstood subject. There is good and bad cholesterol, and new research is indicating that even those divisions are not correct. Every cell in our bodies use cholesterol, it accumulates on the surface of our skin, and when the sun hits it, vitamin D is produced. People who take cholesterol lowering drugs get a vitamin D shortage.
We would die without it. Eggs have cholesterol, but also lecithin, which helps in digesting cholesterol.
So as usual, moderation is the key. It is best to keep the amount of all animal products low compared to the vegetable products we eat.