Bruce was the most active manager in the transfer window in the Premier League this summer, but his side has so far failed to win any of their opening three games.
"There is a huge expectation after what we did in the summer," Bruce told reporters.
"We have not had a good start. OK. [But] why should we take knee-jerk reactions - Like finding my future questioned after two games? I find that very disappointing.
"I find some of the mass hysteria that has engulfed us pathetic, to be honest.
"It engulfs you with two results. It's really, really disappointing. I find some of it ridiculous.
"That's why so many managers have sat here and found it so difficult. Thankfully, my chairman and the owner do not have that same sort of knee-jerk reaction.
"I think some people have got an agenda against me, that's how it looks to me at the moment.
"I understand the disappointment of losing a derby.
"Some of it has been unjust and unfair, but I know for a fact we will not be derailed from what we are trying to achieve.
"We are just an inch away from it. We have the nucleus of a very good squad."
Sections of Sunderland fans voiced their frustrations after losing to Brighton in the League Cup without fielding a recognised forward, though Bruce has called for patience with his new teenage forwards Connor Wickham and Ji Dong-Won.
He added: "When they are ready, I will unleash them.
"It would be wrong for me to throw them in at the deep end when things are going wrong - suddenly, it is an uphill battle for both of them.
"These are two boys we have invested in for our future. With Connor Wickham, we have to be patient. He is 18. Still could play in youth team. We paid a lot of money and he will be an exceptional talent, if given time.
"It was always my fear, bringing him here, that because of the £8 million fee, he [would be] rushed in rather than let him develop. If he is allowed to develop the way he should, he will become some player.
"Asamoah Gyan was sick the other night [against Brighton], not 100%.
"We need to get him up and moving again. But I still do not think he is 100 per cent over the hamstring he suffered against Wigan last season.
"The more he trains and plays, the better he will be and I am still convinced he will score the goals that can make a difference."