Whether it is justified for FR to charge for interviews is a 2 sided argument:
1.) Yes - it cuts down timewaster applications by 100% and stops pilots from getting free training and then finding a job elsewhere. Also, the huge expenses are covered and can be put back into the organisation, from which these pilots will benefit in the long term.
2.) No - no other European airline operates a policy of similar charges and FR should not be using these difficult times to their advantage.
Of course FR should not be prevented from advertising on this site - everybody has the freedom of speech and at least someone guarantees there are actually jobs out there.