I don't see how you can distinguish the two? For a ethical belief that has direct practical implications (e.g. "eating animals is bad"), you can accuse someone of being hypocritical by pointing out that they don't actually act that way (e.g. they eat a lot of meat). But the repugnant conclusion isn't directly applicable to practical decisions - nothing an individual can do will change the world enough to bring it about, and the repugnant conclusion doesn't directly imply anything about the marginal value of quality vs. quantity of lives.

If you mean you don't believe I would take practical steps that favored the supposedly repugnant conclusion if I had a choice, then you are mistaken. For example, I am opposed to the use of contraception because it keeps population lower, and I would maintain this opposition even if it were clearly shown that with the increasing population, the standard of living would continue to decline until everyone's lives were barely worth living. This affects me in practical ways such as what I try to persuade other people to do, what I would vote for, what I would do myself in regard to a family, and so on.