The struggling Suffolk side had to come from behind after Lee Tomlin's early strike and needed a DJ Campbell penalty on the hour mark to secure a share of the spoils.
McCarthy said afterwards: "It was a point won (rather than two lost). I haven't seen their goal again, to pick the bones out of how we conceded it, but it looked another soft, milky one. They scored too easily.
"We didn't play well in the first half and couldn't pass it to our own team-mates, but towards the end we were getting better.
"The crowd were right to boo us off at half-time. I didn't have a problem with that. But thankfully we did improve in the second half and played with a bit more intensity.
"We'd been poor, but there was definitely a response from everyone in the second half, from the players and the crowd. We deserved a point, that's for sure, and I thought it was a stonewall penalty.
"The game became really stretched. In trying to win it, we were in danger of losing it. Our passing was nervy and awful at times, but in the second half it was much, much better."