The article overplays the alarmist tone a bit, but this is still an idiotic experiment.
If I understand correctly (the reporter didn’t explain it properly), he mutated the virus multiple times, until it no longer matches existing antibodies (i.e. somebody exposed would still become resistant — if they survived — and it is still possible to create new antiviral drugs that can target it); i.e. it is dangerous, but not invincible.
Given how long it takes to make new vaccinations for flue strains (and the cost of distributing them globally), this is still deeply irresponsible.
A controversial scientist who carried out provocative research on making influenza viruses more infectious has completed his most dangerous experiment to date by deliberately creating a pandemic strain of flu that can evade the human immune system.