Timothy Mcveigh actually was considered a terrorist by the FBI.

Those don't sound like gang members.

Well, any group or individual that attacks civilian or governmental targets with a political agenda behind them is a terrorist in my book. This should include gangs and a lot of other groups on society.

How can it possible be terrorism within the country if the government sanctions it?

Terrorists have political/religious motivations. I doubt most gangs have such ambitions; they tend to survive through illegal means and violently hang onto their interests. That is criminal, not terrorism.

Terrorism is reserved for acts of violence that would change government policies and/or further one religions agenda at the expense of another.

In this regard, Muslims are taking the spotlight. Have those incidents you listed committed those crimes in the name of Christianity? Were these acts meant to make the governemtn aware of something the killer wanted them to change? If not, then these are criminal acts, and the killers are mentally sick, but not religiously or politically motivated.

Exactly...it seems silly to change the definition of the word "terrorist" just because "gang member" doesn't hold a negative enough connotation (apparently)

The word Terrorism meaning was set to fit Muslims in the context you described. I would say any act taken to terror civilians regardless of the motive should be considered  Terrorism.  In addition,  if you want to put it in the same context described, you can consider American and French revoluations as act of terror....

Not true.....Ireland has rebels that want to change the governent policies, so does Ukraine with the pro-russia rebels. In these cases, they are also terrorists. Good ol white people. Because they have political motivations.

American and French revolutions were acts of terrorism. They had political motivations, nobody is going to argue with that. Was that supposed to disprove my claim?

the ira and the fighters from east ukraine are not terrorists because you just can be a terrorist in democracy.