[Cyphase]

A couple of potential answers:

* It's not about computers and them (Liz and Werner). It's about Cosmo.

* Computer dating is about algorithms and pattern matching. Cosmo didn't have any suspicion of Liz and Werner going on a date; even if he saw a type-mismatch, humans are complex and multi-faceted. But when he learned a computer program ostensibly made the match, his alarm bells went off.

[cestith]

Beyond that, there was already the suspected breach of the site which he knew Bish was interested in breaching. The mere mention of a computer being involved would have made him far more likely to suspect his involvement.