There is nothing wrong with being grateful for said services, but you should understand that Blue Lives Matter isn't just a courtesy or acknowledgement of law enforcement - it exists purely as another "side" to Black Lives Matter, and implies the lives of police matter more than those they take advantage of on a near-daily basis.
It is inherently understood that the lives of police, EMTs, firefighters, etc. "matter" in some capacity, and there isn't opposition to said claim. Creating a slogan like this exists purely as a divisive catchphrase to create a sense of guilt just for merely supporting the fact that black people don't deserve to be gunned down, sometimes literally, by a police force that was originally created to control them.
I don't think its so much guilt as a diversion or "counter" option to drown out the protest.
Its like on the playground if someone says something a kid doesn't like or want to hear, they stick their hands over their ears and yell "LA LA LA LA!" They can't really do that in this situation without looking completely moronic, so they have to take the original message twist it and yell it back to drown it out.
It's like a subtle version of the tune out but still not too long a distance away from the same level of immaturity.