If you call users (direct or indirect) unfriendly, unwelcoming, snappy, rude and contemptuous that will certainly not help forum's atmosphere.
Actually I think it will. If the forum and its members are not constantly reflecting on what they say and how they act, then we will not be serving out the purpose of this forum. We need to be constantly reassessing how we say things and what we say to members, both old and new, as well as holding other members accountable through criticism. If we aren't constantly reinventing ourselves and listening to the comments of our peers, then we fail to grow as members of this forum and as people. So yeah, initially, it won't help the forum's atmosphere, but ultimately, it will lead to a net improvement as people accept the criticism and work to improve themselves and the forum's atmosphere.