Is it permissible for the nieces not to meet their paternal uncle because of his obscene jokes?

The nieces must not uncover their faces to their paternal uncle, nor should they approach him, because his immoral jesting raises suspicion and there is a fear of fitna (strife/temptation) from it. Scholars have stipulated that for it to be permissible for a woman to uncover her face to a mahram (unmarriageable kin), there must be no fitna. They must keep their distance from him and not uncover their faces to him as long as they observe from him this ugly jesting that necessitates suspicion.