For the similiar reasons as to why IBD folks aren't suppossed to take asprin or NSAIDS anymore, it's about gut-health. It also depends on which doctor you ask. See Wikipedia's defn of Loperamide for a full explaintion regarding contradictions and adverse effects.
Rather than using another chemical medicine, It is better to use absorbing foods such as saltine crackers and minute rice, according to nursing studies in relation to both colo- & ileo- ostomates.
And, again, it's a matter of personal belief.