Being welcomed generally feels good. When one is given an ultimatum to choose between friends, or between sets of friends, some find that to be a rather unpleasant feeling. I personally see it as creepy and manipulative.
“I like you and want to associate with you.” is, to me, a very positive statement.
“I like you and want to associate with you, on the condition that you not like or associate with so and so.” is, to me, a very asinine statement.
The former is welcoming, the latter is not.
