The reigning Super League champions won 20-16 as they made it 14 successive home wins over the Airlie Birds.
However, they had to dig deep at the end as Hull threatened to overhaul a 14-point deficit.
“I thought it was a good contest in the main and ultimately I thought it was our defence that got us it,” said McDermott. “We were very strong defensively and we weren’t far off in attack.
“I am pretty proud of how many times we kept them out. We were good value for the win.
“I thought it was a good reaction to our loss against Widnes.”
Scrum-half Richie Myler was man of the match with a controlled performance, having a hand in three of their tries and hurting Hull with his kicking.
“He is starting to strike some onfield relationships with players now,” said McDermott.
“He is having a good influence on us. We are in good shape at the moment. We have played five games, one of them being the World Club Challenge, and are looking forward to the next few weeks.”
Hull were aggrieved a Josh Griffin ‘try’ was disallowed due to a debatable obstruction just before the break when trailing 10-6.
Coach Lee Radford said: “Some weeks you get them, some you don’t. It’s swings and roundabouts. Hopefully it will swing in our favour next week.
“The decision was made by the letter of the law and the lead runner got on his outside shoulder.
“Sometimes there’s grey areas and we didn’t get the call.
“We’re devastated with the loss, but really pleased with the effort and endeavour.
“There’s some real fine margins in the game and unfortunately we just fell short.
“Nine of those players came through our system and there’s 12 English kids in there.
“Jordan Lane, at 19, looked really good on his debut, too.”
Hull were 10-0 down early on against Leeds’s fast start.
Radford added: “We showed them the Super League semi-final of last season (that Leeds won) and the start and how quick they were out of the blocks.
“We spoke all week, identified it early, practised it enough, but just couldn’t come up with an answer.”