What is acceptable is a matter of personal prefernce and where the photo will be used.

I personally think that the flare is well within the tolerance of being acceptable. When it comes to needing the lens protected in a harsh environment, such as ocean spray or possibility of objects, this protection is crucial.
I have seen much worse flaring with cheaper filters was are intolerable for my personal preference.

If you were doing photos for a stock photography site then would not be considered acceptable as it highly visible. Then again, stock photography sites are strict on many more factors besides flare.

If it is for Facebook or any other social media site, most really won't notice that level of flaring unless they are like me and see every facet of the photo in great detail.

There also is a matter of uniformity of the color behind the flare.
The white wall behind this photo is uniform and color and texture. So, it is more apparent than having a flare that is more hidden away in leaves, for example.

No filter is perfect, you will always be balancing the choice of quality versus protection.

An addendum, multi-coated filters are better to reduce such flare.