As an onlooker, it appears some Evangelicals may be the ones who are bothered that others believe something they do not--or believe not important.
In my opinion it is a sin against God--and presents a travesty of God--that one is in danger of hell by not accepting Jesus as Lord and Savior. It suggests that God's love and power is limited and that God builds borders and sets traps for the faithful with other religious/spiritual beliefs. In short, it is our blasphemy against God and His Holy Spirit, not blasphemy from those of other faiths.
Evangelicals and their "personal relationship" while understandable, can also initiate a gag reflex. It suggests that an individual and Jesus are buddies. I believe a better description of a relation with Jesus, with God, is a respectful one where the relationship is one of mentor and student, redeemer/forgiver of those slips we make as we journey through life. It also suggests that you see Jesus only as he relates to you personally, instead of being awed and respectful that we are a flock with one shepherd who is looking out for all.