Porter came out to argue that decision, one night after Paul Clemens was tossed without warning for hitting the A's Jed Lowrie.
"My response to [Baker] was real simple," Porter said. "If you're going to toss our guy yesterday, then it looked pretty intentional to me. It's a judgment call on the umpire's part, and he didn't think it was intentional. I said my piece, what it is I thought, and he threw me out of the game."
With that heated exchange, the second-year manager was booted, the final frustration on a night in which the Astros surrendered seven runs in the top of the ninth after playing Oakland even through eight innings.
The A's Brandon Moss was plunked twice in that same ninth inning, leading off the inning in a tie game and with two outs after Oakland had plated seven runs.
"I know that they weren't on purpose," Moss said. "If you're going to hit somebody, you're not going to do it in those [situations]. I understand what they were doing. I stand kind of close to the plate, and in those counts they were trying to come in. They missed and hit me."
That acknowledgment made Castro's hit-by-pitch all the more curious.
"I don't really understand why they were so upset. …We're not trying to extend a seven-run inning any longer. I thought that was pretty weak," Castro said.
"Obviously, they were pretty upset after Moss got hit again after [Josh Donaldson's] home run. They were yelling from the dugout after it happened, so I was not too surprised that [my hit-by-pitch] was coming."
The ejection was just the latest twist in a weeklong drama between the teams, one that Porter refuses to acknowledge but Lowrie has called "stupid and embarrassing."
It stems back to last Friday's game in Oakland, when Lowrie laid down a bunt against an Astros shift in the first inning with the A's already up, 7-0. Clemens and Porter took exception to that, with Clemens later throwing near Lowrie and Porter jawing with the A's shortstop.
The emotion has carried over to this series, with Clemens getting tossed on Thursday for hitting Lowrie with a pitch and the teams trading more words -- and plunkings on Friday.
"Whether I got hit twice or not, they've hit us a few times this series," Moss said. "I know we hit one of their guys. I think Bo said it yesterday. The game of baseball takes care of itself, and that's what happened tonight. Some people might not like it. Castro might not like it. But stand behind your words."
It was Porter's first ejection this season and the fourth of his career. The teams are just halfway through a four-game set in Houston.