Speaking louder and faster never makes your point any better or stronger. It makes you sound pushy to say the least.
You might do it unconsciously, especially when you are excited about your idea. Note, that more often than not, your excitement clouds your vision to see the loopholes (that can potentially work against your idea).
Let others speak, even if you think they will take a direct dig at your idea.
Side Note: If you think they are taking a dig at you instead, its a different battle to be won or lost.