"The only way that antibiotic resistance arises is if some bacteria happen to have a mutation that confers antibiotic resistance before exposure to the drug."
This is the quote from your textbook which clearly states that antibiotic resistance is a real phenomenon.
Its merely stating that the antibiotics only allow for survival of the bacteria that are immune to its effect. This is clearly differentiating this from the misunderstanding that bacteria mutate in response to antibiotics. They don't.
This is natural selection. If they have the right mutation, they outlive the antibiotics and then can only reproduce other bacteria like themselves. The old strains of bacteria are gradually replaced in the population by the new antibiotic resistant ones.
The text passages are mainly describing how antibiotic resistance occurs which is not reactive to anything in the environment, like antibiotics, but passive in that only the bacteria that can survive the antibiotic will survive the antibiotic. It is not questioning the existence of antibiotic resistance.