Yes, people who are active over here would quite often find themselves being denied visas to enter Vietnam. There are numerous cases of people, even after getting a visa to enter Vietnam, getting stopped at the airport and getting sent back out right away, numerous times. I can cite you numerous cases of people who are active out here and go back for family visits. Maybe their mother or father passed away and they go back for the funeral. They get picked up by the police, questioned, held for a few days, and deported. It's very common. Vietnamese Canadians, Vietnamese Americans, and Vietnamese Germans all experience that. If you are vocal, if you are active, you will experience that kind of treatment from the Vietnamese government.
In many cases, their families in Vietnam also get into trouble and are questioned and harassed by the police. It's very common.