You presented the wikipedia article (which contained the image clearly showing two distinct branches) as an argument to begin with. Now it's not good enough anymore?
There are differences between Polish and Russian language. Between Latvian and Russian language - for all intents and purposes - there is nothing common. Oh, but both languages have free-word order!
There is no shared history. Latvia has been part of Germany or Swedish Empire and Polish Livonia far longer than it has ever been under Russian Empire/occupation.
I communicate with people who speak either in Latvian or English.
It seems like you're talking here about the older Russian minority living in Riga. They might be watching Russian TV, who could have thought?
I literally don't know a single Latvian - old or young - who watches Russian TV. I do know older people (>40) people who don't know English well enough (and are too lazy to learn), so they would occasionally watch downloaded American movies or TV-series over-dubbed in Russian.
I think it's pretty clear by now on whose behalf you are posting here. I'm done here.