Praise be to Allah.
We put this question to Shaykh Muhammad ibn Saalih al-‘Uthaymeen,who replied as follows:
If most of the work which this company does is haraam, then it is not permissible for him to do that. If most of what they do is permitted, then it is permissible for him to do it. If they (haraam and halaal elements) are the same, then he should not do it, on the assumption that what is haraam will outweigh what is halaal. And Allaah knows best.