I haven't read MTMTE (I really should get on that), but as for the context...
Through a series of disconnected memories, we see that Megatron was once a champion gladiator, and he was extremely popular and played to the audience, saying that he gets stronger when the audience cheers for him. Bumblebee hero-worships Megatron.
Flash forward and Megatron is a "former" gladiator, making speeches about how he fights for the people and he does it outside of the ring now, and how he won't stop until life is better for all Cybertronians and no marginalized groups will be left behind. Bumblebee continues to hero-worship Megatron. And Optimus is seen standing behind Megatron in support.
Then we see that Optimus has been the one writing Megatron's speeches for him, while Megatron argues with Optimus that talk isn't working and more extreme measures are needed. Bumblebee still seems to be a Megatron fanboy, and doesn't seem to know who Optimus is.
Then after another cut, Megatron has done something, but it's not clear what he did. Optimus is pissed off by it, and he storms into Megatron's place, with Bumblebee accompanying. It's seen that Megatron has Shockwave conducting Frankenstein experiments. Optimus tells Megatron to cool his jets and return to the path of peace. Megatron tells Optimus that peace won't change things for the better fast enough, and says that temporary war is less costly than prolonged injustice. Optimus says he'll stop Megatron. Megatron says to bring it. Megatron then offers to let Bumblebee join in his crusade, and Bumblebee (formerly a total Megatron fanboy) says "Hell no, I'm with Optimus here. You're fucking crazy."
After another cut, Bumblebee is captured and taken before Megatron. Megatron reveals to Bumblebee his plan to use the AllSpark and Vector Sigma to create a new world full of people who have been engineered to agree with him and follow his orders, and genocide everyone who doesn't, and Bumblebee tells Megatron that Optimus will stop him. Megatron then rips out Bumblebee's voice box so he can't tell Optimus what he's learned.