During a trip to Southern India one man was chanting prayers with his (plastic) shoes on, because he was travelling.
Some local brahmin strongly reprimanded him for his misconduct and disrespect during a prayer. He said the pilgrim has no idea what the prayer is, and is totally ignorant etc.
This was all happening on an empty street early in the morning, not in the temple, so the answers here does not answer my question.
The pilgrim was a westerner. Probably he was chanting "Hare Krishna" on beads. I didn't hear much, but he was relaxed before and then became unsettled, took off his shoes and carried them in hand. So in what way does shoes affect a person while he is praying?