After midweek cup goal hero Ryan Williams had given the Shrimps the lead, veteran striker Karl Hawley levelled for the visitors with his first goal for his new club to earn a share of the points.
In the final moments Gulls defender Dale Tonge was sent off for a second yellow card and Morecambe almost took advantage when, with virtually the last kick of the game, substituteJoe McGee hit the post following a swift counter attack.
"I'm hugely disappointed because it just wasn't good enough," said Bentley.
"We started off the game really well and were on top for the first half an hour but we took our foot off the gas after that and I could see them coming back into it.
"After we scored we really should have pressed for a second goal and maintained the pace but we just didn't do that. I had a bit of a go at the lads at half time because I could see what was happening, but we just didn't respond and lost our shape.
"To their credit they kept going to the end and we could have won the game with the very last kick of the match.
"Overall, I'm not happy but on the plus side we have our first point of the season and it gives us something to move forward with."