No, the phrases "Due to respect" and "To be honest" do not necessarily bring negative content to the other side.
The phrase "Due to respect" is often used to introduce a statement that is intended to be respectful or polite, such as "Due to respect, I must decline your invitation," or "Due to respect for your feelings, I didn't bring up the topic."
Similarly, "To be honest" is often used to introduce a statement that is intended to be truthful or candid, such as "To be honest, I don't think the project will be finished on time," or "To be honest, I wasn't really interested in the movie."
While the statements that follow these phrases may sometimes contain negative content, the phrases themselves do not necessarily imply negativity.