There's too much of anything in food terms. The body can only tolerate a certain amount of any Macro or Micronutrient, because every part of the human anatomy has an upper processing and / or tolerance level, beyond which food wise, there is increased long-term health risk incidence, from regular consumption of the nutrient(s), or at least in some instances, ingested nutrition being expelled via waste products or vomit, which is the lesser of two negatives, compared to the increased long-term health risk incidence.
14g protein from a protein enriched bread is not excessive no. It's only 56 calories of Protein in one go. I think your body would probably be able to handle around 2x that roughly, before any more Protein in one sitting became unusable.