SHAFAQNA – The Grand Ayatollah Sistani answered questions about socializing with people who do not perform Salaat.
Question: Is it allowed to perform Salaat and eat in the house of someone who does not perform Salaat?
The Grand Ayatollah Sistani: There is no problem.
Question: Is it allowed to socialize with people who we know do not perform Salaat?
The Grand Ayatollah Sistani: There is no problem, but with the probability that prohibiting bad may be effective, or even according to Wajib precaution without the probability of any effects, it is necessary to express your disapproval (that they not perform Salaat).
Source: PERSIAN SHAFAQNA