It's 1g per lb of lean weight. That would be for a beginner, trained athletes aren't going to be putting on so much muscle so won't need so much protein.
there is no disadvantage to consuming too much protein.
Uh... there are many sources that cite problems with eating too much protein. Dehydration, kidney stress, calcium deficiency, heart disease, and other side-effects of increased fat or cholesterol levels of foods with large amounts of protein.
None of those links actually cite a disadvantage. In fact from the second:
"Finally, the authors reiterate that even if you consume “unnecessarily high protein intakes” like 1.3 grams per pound of body weight per day, this still isn’t a risk to your kidneys unless you already had kidney disease."
Correct on the steroids and fasting though.