No. Nicotine is a carcinogen. Forgive my surprise, but I'm absolutely blown away that this isn't common knowledge in 2017.
Edit: I appreciate the distinction that folks are making as far as what constitutes a carcinogen. Yes, the science we have today falls short of us classifying nicotine as a 'complete carcinogen'. If that makes you sleep better, then ok, but the science shows carcinogenicity in vitro, and substantial ability to promote tumor growth, metastasis, and recurrence in vivo [0][1][2][3].
Your friend is also potentially exposing himself and those around him to formaldehyde and diacetyl and so on, which is present in many e-cigarette liquids.
Folks: eat healthy, get a bit of exercise, read good books, and most of all, develop relationships with people you truly trust. If you find yourself needing to rely on smoking or drinking to get you through the week, take a step back and garbage-collect your life and decide if you're living the life you want, or if it's a life that's in need of radical restructuring.
[0] doi:10.1371/journal.pone.0007524
[1] https://www.ncbi.nlm.nih.gov/pubmed/7848904
[2] http://www.mdedge.com/ccjm/article/101393/adolescent-medicin...
[3] doi:10.1158/0008-5472.CAN-14-0681